You can try mapping several buttons to the same key, i.e. have whatever you need to hold all set to "a", or you could use a gamepad. Either way should work fine.
It should be noted that keyboard mapping tends to be TERRIBLE. It's different on pretty much every keyboard I've used. On my laptop, I can play okay using "sdfg l;'p ah enter ,", but on another keyboard that just doesn't fly. Keyboards don't let you use too many buttons of the same grid or something, but they're all set up differently. Some are all on one grid, some section off by area or hand, some may separate by numbers and letters or something I guess. Other than that, all I can really tell you is you're going to have a tough time figuring out an okay mapping. Your best bet is finding a good USB controller.