Do I need an engagement ring to propose?

No , If the girl loves you enough she could over look the enagement ring. But later she may want one to show her friends . It kinda of romantic when a guy does a implusive thing and pops the question and you use whatever is around you as a ring like one from the little machines at Walmart lol .. and tell her you will get her one later . I'm sure she will love you no matterwhat you have ...