My roblox shirt sleeves don't line up with the torso

Testing doesn't have to cost you the upload fee each time. Upload the image as a plain decal, which is free, then in Studio put a Shirt object on a dummy and paste the image id into ShirtTemplate. You see exactly how the sleeves wrap and can fix it before you pay for the real clothing upload.

you're probably drawing each sleeve square as if it were its own picture. the arm on the template is unfolded into front, back, left, right, up and down, and the 'up' square is the top of the shoulder. a pattern only lines up if it carries across the edges where those squares meet on the actual arm. easiest fix is a plain colour or a pattern with no obvious direction on the sleeves, then check it on a dummy in studio before paying the upload fee again.