I had the walking foot on my machine from a previous project and because I was too lazy to change it I just left it on for this project. It worked really well and the next time I'm sewing with knits I will specifically put the walking foot on. I also used a ball point needle which was helpful.
Of course the shirt is far from perfect. The bottom hem is clearly wonky, but I'm at least feeling more confident and maybe ready to give it a shot with some nicer fabric.