the most common ones to go for seem to be
cv-1 which you should not get anymore due to the cable being a piece of shit
rift-s which is okay but is limited by you needing to get new lighthouses to enable fbt
quest 1 which is okay because it came out before zuckerberg took a steaming pile of shit on oculus (cable enables it to be viable, still requires new lighthouses for fbt)
htc vive, the easiest way to get to fbt due to lighthouses being compatible with the vive trackers (pucks)
index / knuckles, the current stable trademark of quality, the go to for most who want up to date fbt compatible headset with lighthouses, the downside is knuckles controllers being a bit rubbish at times due to them being brittle but the valve customer service is excellent so you can just RMA them and get a new pair if they shit out on you
there are also some WMR headsets out there but most mixed reality headset makers abandoned the regular consumer market and went for corp, make sure it is compatible with vrchat before buying a headset because WMR's are hit or miss in wtf you're going to get