Well concidering that you plan on breeding all your geckos, the cost and food consumption will grow. I just started breeding dubias for my 5 leos because im doing the same thing that you are, starting with the five and then breeding.

Dubias take nearly no upkeep cost at all. You can house them in a plastic tub, get free eggcrate from a grocery store or walmart, and basically you feed them the extra stuff you have around the house. You dont need substrate at all and cleaning is simple.

Buying dubias is cheap if you know somebody already breeding them. I started with 1 male and 3 females that a friend gave me for free. They breed fairly fast and grow quickly. But you could probably pick up enough to start breeding for $5-$10.

Also they are healthier for your geckos than mealworms