Hello and welcome to the forum! Adorable puppy you have there. For the first couple years your pup is growing. You don't want to ad mass to a young dog. Once the dog grows up more you can start exercising him that will help build natural muscle. You don't want to use muscle enhancers, those are not good for the health of your dog IMO.
You can start the raw diet now, BUT it needs to be very balanced and have the right percentages of meat, bone and organ. If not done right he could develop deficiencies.
Read up on the Prey Model Raw diet ---just google it.
First thing I'd do is take him to the vet for a check up unless you already did that and make sure he is parasite free.
and of course get him vaccinated.
I'd avoid going to Denver if I were you as bull breed looking dogs are banned there (just in case you aren't aware) I lived most of my life right near Colorado Springs!