Teespring Listing Issue..

I've trying to add several pieces of merch to my YouTube channel's Teespring store but it's not letting me add a third. Does it limit you to only 2 designs until you make a sale? It's saying "Before you can add more, add a payment method." But I can't add a payment method because it's not letting me do it until I make a sale. Pretty annoying tbh.

I was trying to put my most popular designs from Redbubble on there because they connect well to my YouTube stuff and I figured it would bring some sales, but I guess Teespring is like "No, screw you, you only get two." Which sucks, because it means I can only put ONE design if one is a dark version and one is a light version.

Anyone else run into this issue? Also, if I am going to be limited like that… What have your best selling items been? I figured Classic Tees, Mugs and maybe phone cases and stickers would be my best bet. What has your experience been?