gems for newbie

hi im newbie im in lvl 70 i just want to ask if anyone has a strat to earn gems solo? like i dont need to win i just want some decent gems at and decent wave reach least i always die around wave 12 and the gems i got only around 13 or 17 i forgot, i tried to look on yt but the enemies now in game is different so anyone know new strat? i want to play solo because i dont want to bother other players trying to win on HC queue TYIA!