Considering I have experience making t-shirts, here is some help.
For T-Shirts I personally recommend either Heat Transfers or Silkscreen.
Heat Transfer is essentially a print out of any design, logo, or picture, and ironed on a t-shirt at 400 Degrees.
Silkscreen is done on almost all commercial T-Shirts that you buy at the store.
If you want a polo shirt, the Only thing that I can recommend is Embroidery.
Silkscreening is very expensive in low quantities... it becomes very cost effective over a large amount of t-shirts.
Heat Transfer is great if you need between 1 and 25 shirts.
Embroidery can be done on lots of items and looks great, but comes expensive if you need a logo. Something like the AnandTech logo will cost about $50 to make into the right format.
if you have any questions just PM me or IM my AIM screen name.