I would take the time to add in organs before other kinds of meat. He will need organs in his meals soon, especially now that he is adjusted to the chicken. Once he's doing well on balanced servings of chicken muscle/bone/organ, then I would look seriously into adding more varied proteins one at a time.
There's nothing wrong with chicken being the primary protein. That's the base of Kaiju's diet because it is cheaper that way, but I do work in a good amount of other meats. His diet right now is probably 50-60% chicken and 40-50% other meats. There's nothing wrong with ground. I find buffalo cheap ground, so that's what he gets. As long as he gets something else that has the bone, like some ground turkey and a bone-in chicken leg, he'll be fine.
Supplements are largely up to you. Personally, I just feed a garlic flea and tick preventative, cold pressed coconut oil, and a little bit of goat milk every now and then. You could do a glucosamine/chondroitin supplement, but I like to use natural sources. Any cartilage rich animal parts will have a lot. Kaiju gets a lot of chicken feet and cow/pig snouts that I pick up at the asian markets cheap. Certainly much cheaper than the cost of a supplement! When looking at human supplements for a dog, know how many mg they need of whatever you're looking at because they probably won't be balanced for a dog. Especially fish oils. There are a lot of human fish oils that have too many omega-3's. Too many omega-3's in a dog's diet without enough omega-6's can actually cause inflammation.