I would buy some ks items I don’t have like a brac scroll or a g1 brac, a golden unicorn, and a Grimalkin. I’d also buy loads of custom apparel and besprinkle my wolves. I want to buy more apparel, but I’m always broke because I keep buying more wolves!
If I had 9,999 moonstones, I would likely expand my den for sure - but also use some in the flea market so other users get to have more moonstones as well. Other users put out really pretty wolves, so I know I'd find some in the market I'd love.
I'd try and snag a golden unicorn, then blow the rest on sprinkles. I don't even want triples or quads, just pretty combos for all my wild wolves and g1 bracs.