Hi.
Yeah, I'm a first time garter snake owner as well. My little girl is a Western Terrestrial Garter snake. I'm very surprised about how fast she has gotten used to her new habitat since she is wild caught. I've had her for a week and she just ate her first worms a couple days ago
I reccommend starting with bigger worms, or feeder guppies. I know this might seem a little gross, but you can also try cutting the worm in half which will make it more appealing to the snake. My little snake can't resist a crazily wriggling worm
I'll be getting some fish for my snake as well. I've choosen to get Rosey Red Minnows a.k.a Tuffies or Big Headed Minnows. I've choosen them over regular feeder guppies because some people sneek in baby goldfish (which you shouldn't feed) with the guppies. Also, the feeder guppies are usually more likely to be sick and carry harmful parasites. I chose Rosey Reds because they have less bones, and are pretty on the eyes
and they are still very resonably priced.