American here, so my preferred sources might be different than those across the pond, but here are my thoughts. If you're looking for armor in the strictest sense (particularly for wedges),
grade 5 titanium is what is most commonly used in beetleweights since it is strong/flexy to take impacts while being lighter than steel. For frames, many people use impact resistant plastics like UHMW polyethylene because it helps to absorb impacts and tends to flex/scratch when hit rather than breaking (one experienced builder recently
built a 30 pound bot out of a slab of the similar HDPE that the Brits seem to prefer). For lids/baseplates there is much wider variety with everything from aluminum to polycarbonate to garolite seeing frequent use.
Weapon motors very commonly come from HobbyKing, with the
Propdrive series seeming to be notably popular at the moment. For drive motors I would recommend
Pololu,
ServoCity, and
FingerTech.
As far as tools go, I've been doing fairly well with basic tools like a drill, jigsaw, dremel, sander, and metal shears supplemented by having a couple more difficult parts
cut by waterjet. You don't have to have a fancy CNC mill or lather to be able to make a cool bot, you just have to be able to design around your tool limitations.
As an aside, this forum has become much less active than it used to be, but there is a very large and active
group on Facebook that you could join.
