Very Best Diet?

You'll get tons of different answers because so much depends on the gecko you get and it's living situation. Warmer temps mean faster metabolisms and cool mean slower. Geckos that will be bigger when they finish growing will more than likely grow faster. They will also eat and grow too fast (in my opinion) if you feed them as much as they want.

I feed my geckos 3 times a week until they are 40g and then 2x a week after that. I feed mainly mealworms and give them 10-15 each feeding. Every other week I'll give roaches instead of mealworms and I tend to feed more super worms in the winter when I don't have tons of babies that need mealworms. They get 2-4 appropriately sized roaches or superworms instead of the mealworms. I don't really feed crickets but I would probably give 7-10 large crickets in place of the mealworms if I did.

There are plenty of hard facts. Nutrition is nutrition, it's the same as preferring one dog food to another. Or on flavor of cat food to another. The rule of thumb is : Feed your pet what he/she can consume in a 15-20 minute time period. It's just like any other animal including humans if we eat too much we gain weight, we eat too little we lose weight. There is no perfect diet everyone and everything is different and we all require different foods.

The best diet is one filled with a variety of properly gutloaded and dusted insects. The more often you can switch it up, the better. I think most folks use mealworms out of convenience, not because they are the healthiest staple.

Healthy insects, can be rotated in frequently:
- roaches
- silkworms
- black soldier fly larvae (Phoenix Worms, ReptiWorms, Calci-Worms)

Other insects sometimes used as staples:
- crickets
- mealworms (all stages except dark beetles)
- superworms

Insects to be used in moderation:
- hornworms
- butter worms
- isopods

Most of these insects can be gutloaded with nutritious vegetables and greens before feeding, and all should be dusted with supplements except black soldier fly larva (because those are extremely high in calcium).

Frank Indiviglio has written some excellent articles on balanced diets for Leopard Geckos. I suggest you check them out:
What Do Leopard Geckos Eat? - Zoo Researched Diet | That Reptile Blog
Feeding Leopard Geckos - Beyond the ?Cricket and Mealworm? Diet - Part 1
Feeding Leopard Geckos - Beyond the Cricket and Mealworm Diet - Part 2

I can get Super worms, mealworms and crickets on a regular basis ... I will look at what else they have and ask before I buy

I feed my leopard gecko dubia roaches and wax worms as a treat