I wear snug fitting capris. And the big thing for me was (and I can’t believe I’m admitting this) no undies underneath. (Panty lines? Are they a thing anyone else worries about?) On top when I’m feeling confident, just a sportsbra, but most days those tanks that have built in shelf bras. I avoid the ones with ‘cups’, because I figure that’s going to be a weird sweat pattern. Since it’s yoga, you don’t need the same level of support as if you were running, so the shelf bra is more than adequate.
I should note that I sweat like a BEAST, like unholy amounts of sweat, and so clothes that aren’t snug fitting really start bugging me during practice because they get clingy and draggy and gross.