I'm not an expert, but here is a list of the things I found most valuable in redoing the body and chassis of my M-5 truck.
A good, high quality hydraulic floor jack. Don't skimp here - you're life depends on the car not coming down unexpectedly. But, NEVER, EVER lie under any car supported only by a hydraulic jack!
A pair of strong, adjustable jack stands. These will support the car once the hydraulic jack has lifted it off the floor. They should have a wide base so they can't tip. Once you have lowered the weight of the car onto the stands, be sure that the bases are flat on the floor.
Studebaker brake drum puller. This mounts on three of the wheel studs and puts pressure on the center of the axle. Tighten it up and hit it with a 3 lb hammer. You cannot get the drums off by pulling on the outside of the drum; they will break! May cost $75-$100 at a swap meet for an old one, but worth it. J.C. Whitney sells a cheap one.
Lincoln Weld-Pak 100 MIG welder with 75 % argon/25 % CO2 gas feed. Welder cost about $400, gas bottle about $70. There are lots of small MIG welders available for this kind of work. The money spent on the gas saves a lot of slag hammering and lets you do sheet metal.
Auto-dimming welding helmet. With a helmet, you have two hands free. With an auto-dimmer, you can see where the arc will start.
Sears 5 hp air compressor, 60 gallon tank. Works OK, but not enough air flow, buy a "real" 5-7 hp, 240 volt compressor with at least 12-14 scfm flow at 100-150 psi, especially if you plan to do any serious sandblasting. Here is a case where bigger is DEFINITELY better!
Air tools: ratchet driver, 1/2 inch impact tool with a set of deep sockets, cut-off tool and about 20-30 disks, dual action (DA) sander/grinder.
Portable suction sandblaster. A cheap one from Sears or elsewhere will go a long way. Be sure you have a place outside to do this work and let the sand go wherever. Get a hood and a bunch of very good quality OSHA-approved dust masks - you only live once
A sandblasting cabinet for small parts. Northern Tools has them or build one out of plywood. Be sure it has good light inside and a vacuum for dust collection outside. The grit stays inside, saves money and mess.
4.5 inch DeWalt angle grinder with wire brushes, cut-off wheels, 60 grit flap wheel for weld grinding. While you're at it, buy two grinders so you don't spend all of your time switching wheels. Buy some noise-blocking ear protectors while you are at it. The flap wheels are much better at smoothing off welds on sheet metal than the hard wheels. While you're at it, buy TWO angle grinders: one for a narrow cut-off wheel and the other for a flap wheel to finish welds and edges.
A couple of body hammers and dollys. Go ahead, hit the metal, you'll learn how to use these pretty quickly!
A couple of really good work lights that have tall stands, short stands, and clamps to hold them. If you can't see, you can't work!
A nice kneeling pad. Kneeling on the concrete floor of the garage or the wet ground is not fun after a few minutes.