I'd recommend a tight forming t-shirt. We call it a rash guard but many people know the brand Under armor. I'd wear some track pants, sweatpants or shorts. They should be chosen so they don't come off! So something you can tie would be good. But if you don't have any of that just show up in any exercise clothes. Just make sure it is clean. Hygene is very important on the mats.
Don't worry too much on your attire, simply aim for athletic/gym attire such as sweats or shorts (ideally without pockets) and a close-fitting t-shirt or compression shirt.
Loose fitting sweats and shirt.
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