Can you advise me on what scissors or brand of scissors I should buy to cut t shirt fabric?
First of all thank you for contacting me. Sewing Q&A not only helps you but other fellow sewers as well.
To answer your question, I don't believe there are any specific sewing shears that you would use for stretch knits. However, very sharp, 8" or longer blades are best for knits.
As with any product, there are general guide lines for quality and use. However, what works the best is more of a personal thing.
Dressmaker shears range in price. Some products are better than others. I personally use Ghinger dressmaker shears for cutting fabric, and Finny shears for more general sewing purposes. However, there are some that prefer other brands. No matter what choose the best quality you can afford.