Hello! It’s nice to meet you! I’m also 21! The only other places I know (although not sure about the fees) are here, eBay, Michael’s Marketplace(?), local markets and of course making your own site to sell. I also love making amigurumi along with garments and I also love knitting 
As for better on laptop or phone I think it’s just a personal preference so whatever you find more comfortable to use I don’t see much of a difference between the two 
I hope you enjoy it here and welcome to Ribblr, here’s something I try to do when I can for newcomers if you ever need help never hesitate to ask in the community, if you need immediate answers feel free to use the help center, search in the community, or the wiki [link below] testing guidelines and community guidelines if needed Happy crafting! Hope to see your crafts soon as well