Seriously just use the Repashy mix. It's got everything they need, and is much more nutritious than anything you could make on your own.
I used to make concoctions of all kinds for my crested geckos for 3 years, last year I switched to Repashy ONLY and have noticed DRASTIC improvements to health, weight, reproduction, activity, color, hatchling size, more frequent mating, bigger poops, etc etc.
I just use it plain, but you could mix it with some pureed berries or mango or they really seem to like papaya.