the way wheeling works is that it is 90% driving skill, and 10% equipment, fabbing is the same way, a good fabricator can fab something up with limited, poor quality tools/equipment, and a poor fabricator can whip up a scratched, non-square, jagged cut, pigeon-poop welded together set of rock sliders with $100k worth of equipment.
the basics are
1, chop saw i've had the same harbor freight one for 10 years
2, angle grinder with cut-off wheels, grinding wheels, flap-wheels, and wire-wheels, i buy about 1 of those a month from harbor freight, they are like $15
3, wire feed welder, coated wire will get you by, around $100.00
4, if not mig, an arc welder, they won't weld thin stuff well, but can penetrate much deeper in to thicker stuff than even an expensive mig welder
if a welder is not an option for you, many times in the past i have taken my parts over to a muffler shop and said "hey, i'll pay you $20 to weld these pieces together...." they have welders, they know how to use them, and they don't charge the rates of professional welders.
5, drill press
6, if no drill press at least a variable speed drill, with decent drill bits, including step bits, and fluted non-step bits
7, A VICE!!!
8, jig saw, with metal blades
9, a de-burring tool, they are $10 and look like a pen with a crooked blade coming out of it. they de-burr drilled and cut holes easily
10, various styles of vice-grips
those'll get you by but things like angle finders, contour gauges, die-grinders, bench grinders, calipers.....and about a million other things will find their way into your tool box out eventual necessity
