Customers often ask, "What tools should I buy?" Naturally, the only credible answer is "It depends...". Despite that, I want to take a stab at an answer. Here's the broad list for someone wanting to work on their own motorcycle, but it is not a bad start for other mechanical work. I have built this list on my sense of what I use most often. The less often I pick it up, the lower on the list it goes.
Note: Some readers may look at this list and have no idea what the difference is between a combination wrench and a set of slip-joint pliers. For that, I apologize. It is a little beyond the scope of this article. Here's my suggestion: Read tool catalogs. Go to stores that sell tools. Pick them up and read the labels. Dig into a friend's tool box and ask "What's this thing?" Hey, it's what I did. I still do. Nothing is more fun than hitting the tool isle, picking up something unfamiliar, and saying "What the heck is that?!" And education almost always follows.
Believe it or not, #1 on my list is always an air compressor, inflator gauge/air chuck and blow gun. If you cannot do anything else to maintain your machines, at least be able to keep the tires set to spec pressure. The blow gun costs almost nothing and allows you to clean and dry nasty mechanical doodads to your heart's content. A small unit (120 volt, 1 horsepower motor, 2 gallon tank, able to supply at least 2 cfm @ 90 psi) is large enough for most daily needs. That last figure, cfm or cubic feet per minute, refers to the flow rate the unit can manage...i.e. how much air it can pump. A max PSI rating is almost meaningless...and the one that is always shown first on the box. Don't be fooled by a compressor that tries to sell you on a high max psi spec. You never need more than 100 psi in the shop. Flow rate is the true measure of compressor capacity...and flow rate at a specific pressure is the way to compare. 3 cfm @ 40 psi is not better than 2 cfm @ 90 psi. If you plan to buy a air-driven impact gun like they use in tire shops, a compressor twice to three times that size is needed, but battery powered impact guns are making that sort of tool much less popular, so don't sweat it.
But...lots of folks start with hand tools before they ever get a compressor. Walk your own path.
As for hand tools, after many years of experience, it is my opinion it is better in the long run to buy multiple large sets of single types of tools, than you are buying "starter tool sets" that have a few examples of many types of tools (that you must add to later piecemeal). For example, a set of metric combination wrenches (wrenches that have an open jaw on one end and a box-end of the same size on the other) that covers from 6mm to 32mm may have 22 or more wrenches in the set. A starter mechanic's tool kit may have six or eight. A starter set will have a mix of SAE (inch-based) and metric wrenches. If you have a bike from Asia or Europe, it will not have any SAE fasteners on it, so half the set you bought is useless (assuming you don't have other American-made stuff to fix, like I do). BUT, if you are going to buy a "mechanic's tool set", get the biggest one you can afford. It will cost you less in the long run.
And perhaps this goes without saying, but I will say it anyway, buy name brands with lifetime warranties. A no-name brand with a lifetime warranty is no warranty at all. If you cannot find them in 20 years, you are on your own. I recommend JIS Screwdrivers by Vessel. For wrenches, pliers, hex keys, etc. go with Craftsman, GearWrench, Crescent, Kobalt, Husky, and others. For magnetic bowls, picks & probes, punches & chisels, hammers, flashlights, oil pans & funnels, brake bleeders, oil evacuators and and all that sort of miscellaneous stuff, Harbor Freight is a great resource. (I have some Harbor Freight wrenches. Not thrilled.)
So, here's my basic hand tool list, in priority order (yellow items are really high priority).
You can't solve a problem you can't see...
These tools let you tighten and loosen screws of various sorts.
There are a billion different types of pliers that let you grab things that your fingers cannot reach or hold. A single set will generally (and should) include:
Handling nuts and bolts comes next.
Tools to reduce cursing and general frustration...
And some specialized tools made for specific jobs...
For an oil change (even a transmission or final drive gear oil change)...
Some sort of jack, stands or a lift... The right type for you depends on your bike and the sort of work you need to do...and frankly, on how old you are. Speaking for myself, crawling around on the shop floor to work on a bike sucks. I am never going back to working without a lift. But it is clear that a $1500 motorcycle lift is not exactly a starter item. On the other hand, lots of service procedures require the bike to be vertical. If your bike has a built-in center stand and you don't plan to remove the front wheel, you are already all set... but not every bike has one. For many bikes a scissor jack for motorcycles is just the ticket. For others, like Sport bikes (that generally should not be jacked up from below the engine because the pipes are in the way) paddock stands may be the answer. And the rear paddock stand, the swing-arm stand, is always useful for any bike needing chain service. Do a little research into what you really need before you jump to a solution.
And finally, in the category of "Damn, I should have bought one of these years ago!"...all of these can be very useful if not absolutely necessary...although using them tends to require more finesse and judgement than a newbie mechanic may have on hand. Fair warning, be careful with them.
I am sure this list seems daunting and it is by no means complete. I have lots more than this in my shop, but I have had decades to build my collection. Many purchases have been driven by a necessity that arises from a particular project, or the realization buying a new tool solves and old and often repeated problem. I am still buying tools. If I ever stop you can be pretty sure it was because I died. So...this list is designed to get you a good start, not be the definitive list of everything you will ever need. Just remember the home mechanic's motto: "No job is worth doing if it doesn't require buying a new tool!"