My Cuddles is a male Northwestern baby. He's about 2 years old and doesn't look a whole lot bigger than your baby, but it's hard to tell just with a picture. If I were to guess an age I would say 1 or 2 years.

I'm not sure if you've gotten the tank yet, but a little over a year ago my Cuddles managed to escape his tank because the basic mesh lid you get at places like petco was too loose. I was devastated. I've since modified the tank with some cardboard to make the lid nice and snug. Just a couple of dabs of super glue and the cardboard doesn't fall off. It's not the nicest looking thing, but it works and it's an easy way to make sure the lid stays on.

I feed Cuddles nightcrawlers for the most part. I buy those at Walmart. If you live near a Fred Meyer, don't buy their nightcrawlers (especially if you live in Portland). They die quickly and I've found mold in them a few times.
The Walmart nightcrawlers seem to be in better health and have more substance. You can also get worms from your yard or garden, if you don't use chemicals on it. Cuddles loves those. Slugs are good too.

Speaking of slugs, Cuddles (who was captive born and is small) has no trouble eating them, and even likes them. Scar, my full-grown wild caught garter, has tried twice to eat them and totally failed. For some reason he couldn't get a grip on them and just managed to get slime all over his face. He even wore one as a hat the last time I tried.

What really seems to go over well for both of them is live fish. I haven't gotten either to take frozen fish or pinkies. Cuddles is a picky little brat, and I'm not surprised with Scar since he was wild caught. If you can get your hands on some feeder guppies (I wish you luck if you live within 50 miles of the Portland area) or any other live bearing fish, that's a great option.

You really shouldn't need any supplements to go with the food. The worms seem to keep them healthy and happy. I use the fish as a treat, even though they are expensive because I have to buy fancy guppies instead of feeder guppies.

I think that's about all I have to offer in the way of information. I've had Cuddles since he was about a month or two old and he's energetic and temperamental. We rescued Scar in April or May and he seems to be doing fine, other than shedding, but that's because he has a scar that prevents him from shedding completely.

I live in Oregon, by the way. Portland, specifically. I love seeing Oregon people on here