A good rule of thumb that a lot of leo keepers go by, especially for babies.

Feed them as many insect feeders as they will eat in about 15 to 20 minutes. Or until they walk away. It varies from leo to leo. You can also like mentioned above is keep a dish with mealies. You will have to change them out daily with freshly gutloaded mealies.

This is what I went by and mine grew like crazy. Sometimes they will eat a lot other times they don't. I did this everynight by just dropping in a few crickets, leaving them for a few minutes, if they are all gone drop in a few more.

Then once they grew into adults, they eat a lot less, due to the season mine have gone from eating every other day to every two or three days.

Hope this helps,
Kristy