i would honestly say 2cb or mescaline would be the two best for starting. 2cb is nice and shallow and incredibly fun, its just really hard to come by. mescaline can be very euphoric and show you parts of the world you'd never see otherwise, and its not too heavy on the mind in any negative way (at least from what i've heard, i've never had a high enough dose to speak from personal experience).
mda would also be an excellent first.
lsa can be pretty shallow and fun too, so that might also make for a good choice. imo the only nausea from lsa was from eating the hbwr seeds and having to forcefully puke the seed husks up before peaking.