>>49583548 (OP)You're going to have to get used to using proxy shippers, because that's how you'll get the best merch
beginner tier is Amiami, hobby japan, hobby search
toranoana, melonsbooks, mandarake, surugaya, rakuten, mercari, yahoo auction is mid tier. I think a lot of these now partner with proxy services, so it's easier for noobs.
high tier is small specialty otaku stores/websites
most of my favorites don't exist anymore, but if you follow doujin groups on their website or social media pages, they should list the sites they use. You'll have to find these on your own. If you can't utilize proxies and navigate japanese websites, these are too high level for you.