Instagram and Linktree Integration

I have designed t-shirts that I want to sell on my Instagram through Linktree. The link that is on the Linktree automatically goes to the website the shirts were created on which charges the customer cost instead of retail pricing. That said, I want customers to be able to pay on Linktree so I will make a profit. I need tax set up (if necessary) and I would like to accept debit and credit cards, Venmo, Apple Pay and Pay Pal. I am open to feedback on which payment methods are most important. I do have a Square account from another business that I believe is still connected. Please let me know what questions you have. Would like a quote and timeframe project can be completed.