OP, you will have to be patient with books. Doing some research on sold items is a good start. It’s not necessarily bad that you want to sell books that no one else is selling - but the proof will be in the pudding. It costs nothing simply to list, so you might as well give it a try.
Ditch the store, though. You can sell without the ongoing subscription fee of a store. Unless you can see it’s worth it, that store is a deadweight around your ankle.
Re the rest of your post, I cannot see other sellers giving you information sourcing goods. That’s just not reasonable.
Re shipping, do you mean shipping TO you from your current suppliers? Or do you mean postage to buyers?
Re getting products from China, I’ll be frank. I don’t want rubbish stuff from China. If I did, I’d buy it directly from China. I don’t want electrical items that aren’t made to Australian safety standards and that don’t have warranty. And so on… There are plenty of other buyers who have a similar stance, but to ce fair, there are plenty of Australian buyers who don’t mind and who will simply go for the cheapest price.
