When it comes to your t-shirts, you will need to decide what your area of focus will be. Do you want to print using regular ink jet cartridges on
JPSS paper, then the cutter with an optic eye will be necessary. Do you instead want to do sublimation and forget about the cutter? In this case you will be limited to either 100% polyester shirts, Vapor tees are amazing, or 50/50. Another option, if you are starting out is direct to garment printing. If you are handy, there is a thread in this forum on building your own printer for this.
The main thing is, you need to figure out the initial direction for your focus.