You could acquire a .d64 image of something like Merlin and run a C-64 emulator on your PC. That would probably be the cheapest and easiest way to get started, once you've located the educational material (a lot of which could probably be had with some online searching).
8-bitters will probably start an argument about which assembler was the best one. I used Merlin back in the 80s, and it worked fine for me, but there are others also.