Wow, so sorry for this super late response!
I'm trying to get back into being active again, and it's been a while but I am currently working on adopts, so while I'm no expert, I'm happy to share some tips
I always start by browsing the current popular adopts on several of the larger/more active adoption groups. Not only does it show what kind of adopts are selling, but it helps offer inspiration and give ideas for adopts you can make. But I honestly find that when drawing adopts, if YOU really love the design and have fun with it, it shows in the artwork and often sells better too. Drawing adopts is a great way to be creative and make a small profit, but it's more important for me to have fun with it and not be so focused on just drawing something to sell. Aim to price fairly based on the effort, time, and quality of your adopts. And try to keep your adoption rules fairly simple and consistent.
Not sure if any of that is actually helpful or was just vague and obvious, but I hope it helps! And good luck with any adopts you make!
Just let me know if you have any specific questions, and I'll do my best to help!