I can help. Use photoshop and illustrator.
How can you stamp your shirt? If you plan to do for sublimation, no problem I will give you the file in high quality. But if you want to stamp it in screen printing, I think is the best, because they last longer, do not wash away and the colors are more vivid, I can prepare the file, ie not only I give the design, but I give separation, so that you only take her to the shop of your choice and have no problems.
I have 6 years designing exclusively for printed shirts.
(Monster Energy, Energy Rockstars, Ferrari, Baja Racing).
From typography, logo designs to complex images. I know textile printing process and I can advise you to decide what items to use, types of inks, separation processes.
You may want to see some samples on my profile.
I am responsible and I follow up is complete textile printing, and has been of your total satisfaction.
Any questions or concerns, I am in full readiness to help.