For your first heavyweight robot, just go for wheelchair motors + wheelchair gearboxes + wheelchair wheels. Seriously.

does anybody remember this robot ?





Perfect example of a cheap robot, although if you put more time in it it could even look decent

It had wheelchairmotors/gearboxes/wheels, and 1 sidewinder speedcontroller (can be had for 200 gbp) as a drive system, and it frickin rocked. I had so much fun with it, incapacitating BOTH top of the line drive/rambots (storm2 and tornado) in 1 big heavyweight fight, and also putting dantomkia in the pit

So go ahead, get cheap stuff (but DO get a decent speedo) and have a lot of fun !