To make them yourself You'll need ~ T shirts (eBay) $2 Transfer paper (ebay) $20 Printer (your own or if you don't have one use your schools) Now that's just the foundation of the tees I make . You could tie dye them , have cool sleeves or sow fabric on them . Just look online for inspiration . Also galaxy is awesome looking
you can see may online website they provide you may more design and you can design by yourself :)
Try this website, you can easily design tees and make large orders.