What type of ink are you using?
This ink goes well on pretty much any blank distributor but ring-spun fabrics always create the best results so find the best cut and feel you like. Just make sure your printer uses a Poly Blocker ink for you shirts with blended or full Polyester fabrics.
Most brands print well and most companies now use reactive dyes but not all of them do well. A few of my favorites are: ePacific, Spectra Tees, Canvas by Bella, Next Level Apparel and Gildan. Most of these brands have great dischargability with their poly/cotton blended shirts too and the price point is great.
Ring spun cotton garments will be the best due to it's flat & smooth texture along with absorbability for the inks used during the print process. At this time, Spectra Tees is the leading T-Shirt manufacturer for this style printing industry; however most ring spun cotton shirts across the board will be just fine to use.