Boardgame shop

Well laaaads, I'm in the process of doing up a business plan for a tabletop boardgame shop in kildare. I'm just reaching out to see if anyone, who has experience in a similar field or any tips on where to put my focus, could lend a few wise words?

My biggest struggle right now is finding suppliers and estimating the cost of products to myself before they are marked up for retail.

If anyone has anything that might help I would be forever grateful 🙏