There are a lot of diets out there that are misleading. Anything with "pellets" as the main source of nutrition is a diet to throw away.
I'm not well versed on all the great diets, but I use BML. All the ingredients you can get from the grocery store and the vitamins you can get from PetCo. You blend it all together and it can last about 3 weeks for two sugar gliders. You also have to supplement it with fresh fruit and veggies. There are specific fruits and veggies though that you have to use for BML because they make up what is lacking in the mix. Here's the link to that diet:
bmldiet.com/bml-recipe.html
Here's a website that has a ton of information about the other diets and pretty much everything to get you started:
sugarglider.info/gg/
Also, yogurt drops and meal worms(you can find at petco or pet stores in general), and Hersey's white chocolate morsels are great treats, but use sparingly. I give my babies 2-4 worms when they wake up to have tent time and white chocolate morsels to find when I hide them in their cage. Just make sure it's white chocolate without cocoa. That will kill them like it does dogs and cats.
Hope that helps!