You should offer a young tegu food least once a day, it's hard to overfeed a growing tegu so long as you're providing a healthy diet and environment. I wouldn't suggest feeding rats more than once or at most twice a week. The bulk of the diet I feed is lean ground turkey(about 60%), then 20% beef livers, the remaining 20% or so being whatever random stuff I pick up that week(usually something on sale). Here's a good food list to give you some ideas of the variety of foods these animals can take.
http://www.tegutalk.com/showthread.p...#axzz1j0X1ZCyU