Screens
WOOD FRAMES: The least expensive frames are made from wood. These are what I currently use. Wood frames come in varying quality. The better ones have lap joint corners.
ALUMINUM FRAMES: Aluminum frames are more expensive than wooden frames, but will not warp, and will last longer.
NEWMAN ROLLER FRAMES: These are the best, but also the most expensive. These allow you to retension the mesh by tightening the rollers. I have read about the process of tensioning the mesh on one of these, and it is quite involved. If you are a hobbyist, or not really planning to be printing lots of shirts regularly, these are probably overkill.
MESH: Get the screens with mesh already installed. I use 110 monofilament mesh. Mesh with higher numbers will allow more detail. Mesh with lower numbers work better from printing light colors on dark shirts. 110 is a nice middle ground general purpose mesh.
Scoop Coater
You don’t NEED a scoop coater, but it will make life so much easier. Since you will be able to coat your screens with more even coats of photo emulsion, your images will come out cleaner. You want you scoop coater to be about an inch shorter than the inside dimension of your screen. For example, if your screen has inside dimensions is 16×20, you will want a 15″ coater.
Squeegee
Ink
You need to use screen printing ink designed for fabric or textiles. I use Speedball water based ink as it is available at the local art store. Professionel printers use plastisol ink which needs to be cured slightly differently than the the water based ink. The water based inks seem to print just as nicely though, and clean up with warm water.
Photo Emulsion/Sensitizer
I use Speedball diazo photo emulsion/sensitizer, and am quite happy with it. A quart of the emulsion, and a bottle of the sensitizer cost me about $20, and will coat a bunch of screens. If you are only planning on doing a few different designs in the near future, you can get the smaller jar. Photo emulsion has a limited shelf life one sensitized (4 months when refridgerated).
Masking Tape
Timer or Watch
Light
Nylon Bristled Scrub Brush
Transparencies/Vellum