I started racing cross last season, and I do not race anything else, but I commute by bike on the roads. That said, I have interrupters (I didn't realize that's what they're called, but the guy at the shop recommended them and they're great!). I run a single ring up front and I find that it works really well for me. And, last but not least, I use SPD pedals with mountain bike shoes (even on my road bike!).

I hope that helps! Try a few things out and don't feel the need to spend a lot of money up front. Figure out what you like and don't like and then make changes from there. Good luck and I hope you have fun!