If you are interested, I'd also recommend that you check out Michael Essek's YouTube channel (no affiliation, just like his stuff). He is a very successful t-shirt designer who sells books and materials to help people design stuff like this, but he also dispenses a LOT of free advice on his YouTube channel, if you are lucky he'll even critique your design on his show and give you advice on how to improve! Check https://www.michaelessek.com/ or on YouTube at https://www.youtube.com/@MichaelEssek