Welcome. I'm guessing you've read as many care sheets as you could find on the the internet.
The MRP and CGD is essentially the same formula, assuming I know the ones you are speaking of. The MRP is all of the nutrients, proteins and everything else, but no flavor. You choose from, I believe, one of three fruit flavors and mix them together. This has come out of requests of picky eaters and those people that have lots of different species of Rhacs, it is an all purpose diet. CGD is the original specific formula flavored for cresties, and is more often found at local pet stores and in smaller quantities. So, to be honest, it is basically the same thing.
That being said, we only have one crested and CGD has an open bottle shelf life of 6 months so we buy the small bottles of CGD instead of dealing with the MRP which usually is larger quantities.
We believe that crickets are great supplements for babies and juvi cresteds. We would tend to feed crickets about once a week until they are adults, then treats after only. To be honest, when we first got our little girl every book and care sheet was recommending that the crickets be dusted with the T-Rex Leopard Gecko Cricket Dust formula. We were using a general dust for our leo for some time (having gotten her much earlier) so we just switched both of them over to that product. I can't say I did much research at the time and now just do it out of habit, but there is a little bit more to the dust than your average vitamin supplement. Probably not a huge deal, just something we picked up on if you'd like to do your own research.
OK, I don't know if I got all your questions answered, but I hope I took a good first shot. If I missed one, hopefully someone will step in and also feel free to ask as many questions as you like, we are happy to help.
(Especially if you bring crickets)

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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock