Fitness

I think it's best to find a local instructor. When you do it online, you have no one to correct your posture. Also if you really want to practice it as a martial art and not just a health exercise, you need partners to practice with. I use online material only as a complementary resource.

It's also really easy to get lost in esoteric nonsense online to be honest, Tai Chi is associated with Taoism and TCM, and if you go down that rabbit hole, suddenly you find people claiming they can energy heal without even touching others. Just something to be wary of.