I started with a B&D drill and a Workmate bench. Then made a policy to just buy a tool to do a specific job when it came along. No room for a TS etc so I use a circular saw or jig saw using guides made from help on this forum.
This is the evolution of most any workshop, so pick your project first. Thatíll determine your fist tools.
For any project you must measure, mark, cut, join, smooth, and finish the work you have created. It is a given that you will need a work surface of some kind. But that is a matter for you to figure out before you start. Many a project has been built on the ground. Iím too old for that stuff now, but I used to do a lot of work in contorted positions.
A tape measure is usually a good first purchase. Some folks like folding rules, but a tape is quick and stows itself easily. Some sort of square should be next (I used a framing square for years before upgrading to fancier models). You then must determine if you wish to power cut or hand cut. Power cutting usually equals circular saw to start; a jigsaw if your project is curvy. No power equals a hand saw, usually a crosscut saw is a good starting point. Note: While I found that crosscutting was, well, just okay, I found that ripping by hand to be more effort than I was willing to put into a cut... so I went with a circular saw. Buy an extension cord to go with it too.
Joining can entail glue and/ or mechanical fasteners. If your project uses all mechanical fasteners, you will probably want a drill of some kind to A) drill pilot holes (if needed) and B) drive your fasteners (assuming screws). Nails would require a claw hammer. If you need glue, you might consider a clamp or two. Style of clamp will be dictated by the width or thickness of your glueup. Purchase accordingly. Another note: No shop EVER has enough clamps. They will end up being a big part of your shop evolution. I canít count how many clamps I have, of many different styles, but I still always need one more!
Smoothing usually means sanding, although scraping is an option (I suggest sanding your first couple of projects). Right off the bat you would need at least a couple different grits of sandpaper. Iíd start with something like 100-120 and 220 grit. Then you want to figure out if you want to use elbow grease or electricity to do the work. If electric is the winner then I might suggest a random orbital sander in, say, six-inch size. Buy the sander and discs to match each other. I prefer hook and loop sanding discs over the stick-on type, but they are more expensive to purchase. If you choose elbow grease then get sheets and get busy!
Finally, finishing is just what it says. Youíll need either a paint brush or a spray can. Or you may leave your project in the raw.
The little tings like pencils, drill bits, screws and glue will come as you need them. I buy quantities of just about everything, so I always have an extra pencil, some extra drill bits, or half a box screws on hand. Then I replace stuff when I get low.
My last suggestion is to purchase major tools of quality. There are few things more frustrating than a saw that wonít hold square, or a drill whose battery wonít last long, or even a square that isnít exactly square. (Attempt to) Save your money until you can afford what you really want. Youíll only spend it once, and youíll never regret it.