Cis people with time machine: uhh, I'll give john brown some kalashnikovs, I guess
Trans people with time machine: giving 1000 bottles of estradiol to Elgabalus in exchange for becoming co-empress and using your power to establish world communism 2000 years early
Realistically if you got dropped into Elgabalus' court with nothing (and overcame language barrier) you could do HRT with pregnant mare's urine and testosterone blocking with licorice.