I don´t know much about programming on Amiga, but I heard Blitz Basic is a good language to program games in (look at worms for example). Or you can use Amos, but most games programmed in Amos looks like crap.
I think compiling on a bog a500 vill be somewhat slow, so I suggest you get an a1200 with some acceleratorboard and some fast mem plus a HD and a mouse of course
