Hi Kris, and welcome to the forum.

Forget the crickets, Garters don't eat them, alive or dead. The best type of worms to use are night-crawlers. You might also want to use fish and mouse pinkies as staple foods. You'll find a lot of useful information to get you started right here:
http://www.thamnophis.com/caresheets...ake_Care_Sheet
Hope you enjoy it here, and maybe hold on to Rex, even after the spring warm-up!

By the way, what species is Rex? Where in the US are you?