The best for baby leos in my opinion is small to medium mealworms because they are "bite size" and are slower than crickets which gives the unskilled hunter baby a chance at catching it.
I feed mealworms (and occasionally silkworms or butterworms if I happen to get them) to all my juvis because when I sell them I don't want them to be dependent on crickets --some new geckos owners, who are the majority of my buyers, don't want to deal with crickets. Interestingly, most of my adult geckos, including those I hatched here, prefer crickets.