Not sure why the shirt had dull colors, or maybe you just aren't understanding the sublimation process. The ink becomes a part of the fabric, it doesn't sit on top of the fabric and jump out at you.
I have had printed transfers sitting around for months, maybe longer and they printed just fine. You will not have bright or vibrant shirts or any other fabric for that matter, but if you are printing on a hard surface you will have beautiful, vibrant color.
You will need sublimation ink, a dedicated printer, sublimation paper, and sublimation substrates. You cannot print on just anything. Sublimation blanks are specially coated or manufactured to accept the ink.