can i just draw on my t shirt or will i have to pit some sort of layer over it?

Answer 1

There are acrylic, fabric paints, available in most craft and sewing supply stores that will, permanently color the shirt, needing no prepreparation.

Using any other type of pigment may result in a design that fades too quickly, cracks, or may, otherwise, result in a disappointing result.

Answer 2

you could try iron-on transfers, which give you more control over the final results.

You make the composition using a paint program, then print it using inkjet printer, then iron it on.

You can find the transfer material at kmart or other retail stores.