I´ve used t-shirt custom, I have my own t-shirt GVR team. first the easy way to start your custom t-s is print your design at printing shop on transfer paper, if you dont have enough money you can iron it for yourself, be careful no burn it

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I spend about 1 1/4 euro in t-shirt, 2 euros in print my design, if you want a quality in your t-shirt the ironing should be for experts, you would spend about 1.5 euros, so that let us 5 euros aprox.
caution, there is 2 types for thansfer paper, 1.- on time to ironing the tint of paper could be added all the paper size, 2.- on time to ironing just the design should be added. of course the second option is better, i cant tell you how to reconiz them.