Welcome!
The A1200 is pretty much the best option if you're just interested in playing games, but it's hugely expandable as well...
A 50MHz board (I presume a 68030 accelerator) will suit you just fine for nearly every game in existence, and a lot of programs that are available. 4 Megs is good, but if you could expand it, you'll be more at ease when running bigger programs. Most accelerators work with standard 72-pins SIMMs, so it shouldn't be a problem adding some more RAM.
Have fun with you first Amiga! It's never too late to start using them :-)
