It's risky to trade here when the said coin are already on exchange and since you are a newbie you will need a good escrow or you should send first ,doing it in exchanges,lessen the risk of getting scam.
I really agree with your suggestion, if you need XRP, we recommend you buy it at Bittrex because it's available there, so maybe you will not risk big scams, if you want to buy XRP not using escrow, I'm sure you will regret. If you lose your money Because, nowadays many people do deceive this kind of thing.