If you are building cages and need to cope tubes, a chopsaw and angle grinder will be the cheapest route. It gets you close and can turn out decent. The better option would be to get a mill or drill press, chopsaw, grinder. Cut your tubes with the chop saw, use a holesaw to cope the tubes, and then fine tune with the angle grinder.
If you are building racks, bumpers, etc... out of square/rectangular/channel/etc... tubing where you don't need to cope like a round tube, but mainly need angles to line up, bare minimum is an angle grinder with a grinding wheel and cut off disc. It gets you there, but you will go through a lot of discs in the process, not to mention it's easier to shatter those when cutting by hand. Next step up would be your chopsaw, and then a vertical band saw after that.
In a shop I used to work for (we built all sorts of things and did some off road car fabrication/builds, cages, full desert pre-runner, racks, bumpers, etc...) we had a water cooled horizontal band saw, huge vertical band saw, vertical sanders, plasma, chop saws, mills, angle grinders, and some other misc things. When building the stuff you are talking about, I used the horizontal band saw to get the large (20-30ft sections) cut down to rough size, chop saw to get the angles I needed and fine tune the size, and occasionally the angle grinder to fine tune. When building the cages, I used the same process and a mix of the chopsaw and mill to cope the tubes. The chopsaw was quick and dirty and could get close, but the mill and hole saw was the cleanest. The only times I used the bandsaw was when I was cutting pieces of sheet/plate