So i saw the merch t-shirts at the worlds store. What do i need to do if i want to print my name or a logo on it? Do i have to design it online ? And how much does it cost if i print on it (any additional cost?)
They have your team number, so you can just tell them what you want from a list 
Costs for the shirts and jackets are relatively pricy but they are REALLLLY good quality. I dont know about costs in the dollar count because I havent been there for a while, but all I know is that its expensive.
For me, what they did was ask for your team number, and they print it out and add all the customizations right there.