The comfort of the 'lee is paramount, as several people have said, and I look forward to a day when we can all answer this kind of question without enforcing principles that should be a baseline and expected standard for all BDSM play. Siiiiigh
Note: Author is keenly aware of the tragic reality we are not there in 2021 and fully grasps the value of reinforcing "It's always the 'lees choice". Don't @ me with that.
Answering the question: my play partners are split between "casuals", those who mutually enjoy my kink outside a D/s structure and with no inherent sexual component, and "partners", romantic and D/s paradigms within which my kink features.
For "casuals", runner's shorts and a bra is my ideal. Cute, exposing, but still decent.
For "parters", unwrapping them through the session is positively amazing as part of building anticipation. A ticklee in an oversized button-down with a front-clasp bra and underwear that ties on the sides give so many chances to increase their vulnerability in stages and reset their nerve endings by shifting their mental state... that's easily one of my favorite attire options.