I will try to lay out the options to answer every question about which plane to buy, including size, cost, age, material, and primary purpose. I will not go into detail about how to find, evaluate, restore, or use a plane, as I think those are best left separate (feel free to email me questions to prompt an article from me on this topic, although many good answers are already available).
Let's quickly get some terminology and basic facts out of the way first, though.
Planes can flatten, smooth, and level wood, which are three different things.
Flat means in a geometric plane, regardless of orientation or texture, something large planes are good at achieving. A piece of slate leaning against a wall is flat but not level and probably not smooth.
Smooth refers to the texture, or more precisely to the lack of texture. The walls of a drinking glass are smooth but not flat, and if it's standing upright, they are not level either. Any plane with a sharp polished straight blade can make wood smooth.
Level refers to a horizontal orientation, which isn't really what planes are for. The wooden floor I'm standing on in my house is level but not flat because it has sagged slightly over time (and not totally smooth because I have two energetic dogs). If you wanted to level a flat and smooth tabletop, you would apply a saw or a wedge to one or more legs, not a plane to the top. Technically you can level with a plane by removing material from the high side, but usually you want to flatten material, perhaps make the other side flat and parallel, and then position it level.
Any plane can take any thickness shaving
Well, almost. Although certain sizes of planes have gravitated to the roles that usually suit them best, what they can do also depends on how you set them up. The thickness of shaving is up to the user (as is the level of camber, polish, and sometimes the cutting angle). When you own only one plane, you may need exploit this flexibility, and it's a good learning experience. But bear in mind the traditional progression. A medium length plane (e.g. "fore" or "jack") usually takes thick shavings first to get a board approximately flat, then a longer plane (e.g. "try" or "jointer") to get precise flatness, and then something shorter plays the role of a smoothing plane--for eliminating any lingering tear-out, track marks, or other roughness. This combination matches the best attributes of each plane to an appropriate task. But even in this traditional progression, the exact size of the planes, and thresholds between them will vary depending on the project and user. Remember that there are reasons for tradition, but they are not absolute rules.
(For clear instruction in traditional hand plane roles, seek out what Chris Schwarz has written/filmed about "Coarse, Medium, Fine)
So, which type of handplane should I buy first?
This question is more complex than is initially obvious, because you are really solving 3 different problems. You really want to choose a plane that will do all of these things for you:
* Teach you about planes. How to use and maintain them, and what you like to use them for. Any plane (in good working order) can do this although some make it easier than others.
* Be immediately useful. This will give you experience and will give the tool relevance. Versatile tools have a better chance of doing this.
* Find a long term niche in your shop. To be worth owning it should be the best tool for at least one job (for you)--otherwise you may end up wishing you had spent your hard-earned cash on something else.
The best first plane for you will be one that can do these 3 things well.
A block plane is a safe choice for any woodworker.
Teaching ability: The information contained in a block plane is relatively accessible. There is less metal to sharpen (or flatten, if that is required), and these tend to be more affordable than other planes.
Immediate use: A block plane will find immediate use breaking edges, flattening small parts, shaping convex curves, and can even play the role of a smoother plane. It is not good at making reliably flat surfaces on furniture-sized parts, although you can make surfaces that look more or less flat.
Long term niche: Almost any woodworker will have a niche for a block plane in their shop. It's a full-fledged plane that you can easily pick up and wield with one hand. Even those who have a shop full of power tools already will find a block plane to be an extremely efficient way to remove the sharp corners from project parts, flush protrusions, or flatten small surfaces.
Bottom line: If you have any doubts after reading this article, get a block plane first. It's a safe choice that you are unlikely to regret. If you want to stop reading now, just go get the best block plane that fits your budget.
A smoothing plane (e.g. #4, #3, 4 1/2) can be a revelation for those with a shop full of power tools
Teaching ability: Almost as accessible as a block plane, but more optimized for two hands. A fine teacher that will inspire you to get really good at sharpening.
Immediate use: You can use it to "smooth" or refine the texture of a surface, but it can also be used for flattening small surfaces or anything a block plane can do. Will not likely be good at taking off a lot of material quickly (unless it has an adjustable mouth).
Long term niche: As long as you learn to sharpen, a smoother will enable to to achieve the best surfaces quickly. It is the fastest way remove the marks left by other planes, a jointer or a planer. The surface it leaves can be final, or as a prelude to sandpaper if you prefer.
Bottom line: Get a smoother first if you are already using power tools for milling, because using it immediately afterwords will save you time by allowing you to skip most/all of the sandpaper. Buy the one that feels most natural in your hand, ideally with a higher-than-45-degree cutting angle. Then get good at sharpening. But if you are already planning a long trip down the hand-tool rabbit hole, I would recommend delaying your smoother purchase--instead take a little more time to learn your preferences before deciding which smoother to buy.
A jack/fore plane is a good choice if you love hand tools already or want to keep wide stock intact
Teaching ability: These #5 or similar planes are a nice size to get good at two-hand technique. Useful whether sharpened straight or cambered, coarse or polished.
Immediate use: This is probably the most versatile of all planes. It is large enough to do some serious flattening if you need it to, and is also capable of smoothing. But it's best at removing large amounts of material to get a board approximately flat in a hurry.
Long term niche: Doing what it does best, being a fore plane. It's really doing the same job as a powered jointer and planer for those that have a hand tool preference, but it can also handle material of any width.
Bottom line: This is probably the best choice if you have a strong interest in using hand planes, because it will let you do a lot right away while you develop sharpening skills. I would also recommend it to someone who wants to avoid the workarounds associated with wide stock and a narrow power-jointer. I would not recommend a jack plane as an introduction to hand planes for most habitual power-tool users.
A jointer such as a #7 is a bold start if you have large plans and want to avoid power
1.) It will teach you the fundamentals just like any bench plane, as long as you have some large surfaces or long edges to work with. But be sure to get one that's already got a flat sole, or getting it working will be a real pain.
2.) A plane this size, used competently, will end up straightening or flattening whatever wood you apply it to, and is especially useful for dealing with dimensions 3' and larger. You do have some flexibility about what kind of shavings you take, however. It is most natural with a medium thickness shaving (maybe as thick as a business card), but you can take thicker shavings if you put your whole body into it. With careful sharpening, you can reduce the shaving thickness to the point where there is no smoothing left to be done in many cases (a back-bevel may help, too). So it is actually quite versatile, as long as you have the energy to push it around. But it will be hard to use on small surfaces (really, impossible for a beginner on anything less than say, 8"), and you won't be able to remove tearout without removing wood from a large area.
3.) I love my jointer plane, and I have a hard time imagining being happy with any alternative. But folks who are accustomed to a powered jointer don't seem to find much use for them. These will find a home in shop of a person who is dead-set against the noise, dust, and space requirements of large power tools, or is in love with the excercise and ceremony that can come with hand tools. Many woodworkers will be happy without ever picking one up.
Bottom line: The only way this should be your first handplane is if you are absolutely sure you want to get deeply involved with handplanes AND your first application for a plane is something big, like a workbench. If that's you, go for it, and consider spending a couple bucks on a card scraper while you're at it. If you are already content with a powered jointer and planer, don't even consider a buying a jointer plane first.
A shoulder plane is the least-ridiculous type of rabbet plane as a first plane, but you still shouldn't do it
1.) With two more references surfaces than bench planes, and a need for precise adjustment in one additional dimension, these are not an ideal introduction to planes.
2.) As the most versatile type of rabbet plane, this can be used for rabbets, grooves, tenon shoulders. If you really need it to, you could even use it for flattening small surfaces.
3.) If you're going to use hand planes for joinery, this will have continued utility. It has a specialized focus, but can do everything a simple rabbet plane can do too, and that is a lot.
Bottom line) I don't recommend any sort of a rabbet plane as a first choice, because the extra complexity distracts from the most important parts--sharpening and planing. But if you're going to do it anyway, get a large shoulder plane. At least if you do come to like rabbeting by hand and figure out which styles of rabbet plane you prefer, your shoulder plane will certainly be among them.
Other sizes are available.
I didn't mention #1, #2, #6, and #8, but that doesn't necessarily make them a bad choice. What I've covered for the most common sizes should still serve as the basic guidance, but if you or your work is an unusual size, you can use these other sizes to compensate. A #1 might make sense for a small child that can be trusted with sharp objects, or a #8 for a tall person building a workbench.
Bottom line: There are 3 basic sizes for hand planes, not 8.
Consider a router plane if you want, but look to a different article:
Ok, it's technically a plane because it has a sole and an iron, but it's really a different animal because it does not take a consistent thickness shaving like everything else on the list. It might be a good choice if you have the right project, but then you will be back to this article for the second plane, because it's not the same thing.
Now that you know what type you're going to get, let's figure out exactly which one to look at.
Used or New?
Ideally, you want to be able to focus on learning to use a plane, and not be distracted by wondering if it working properly. If you can afford to buy a plane that comes flat and sharp from the factory, I would recommend that as your first plane. I would not consider a new plane that doesn't meet this low bar, because it will almost certainly have flaws that you cannot correct. If you have the skills to restore an old tool, you might as well save some money and get an old Stanley or similar and restore it (but err on the side of a smaller plane). If you have neither the budget for new or the skills to restore an old tool, it gets more difficult, and you might have to make a hard choice between the two. But you also might find an old tool that has already been restored for a decent price if you look towards the kind of dealers that appear at woodworking trade shows. Or find someone local willing to help you restore a plane for the first time.
Wood or metal?
A metal bodied plane is probably your best option, because of the easy adjustment they offer. If you are determined to avoid complexity, you can go with a wooden plane, but you'll have to learn to adjust it with a small mallet. An infill plane is a waste of money unless you are sure you really like planes. And transitional planes are best left to collectors. Bottom line, you should probably get a metal-bodied plane.
Bevel up or down?
It actually doesn't matter all that much. Bevel down planes are a little simpler, a little more ergonomic, and they work better with heavily-cambered blades. Bevel up planes allow free choice of cutting angles and typically have adjustable mouths for ultimate versatility. But you can do everything you need to with either, so get whichever one makes sense to you, and don't regret it.
I'm going to dodge this question, but not completely. Read reviews, and you will find several types of brands. Boutique makers are an OK first choice as long as you can afford it. Brands of questionable quality will probably cost you the most in the end, and aren't worth your time.. What you probably want is a high quality brand with excellent customer service. There are only a few well known ones.