If you consider ethereum and litecoin as altcoins than they are worth buying, they have longterm potential. Never checked ripple before but it looks big so that might be too. If you want more risky ones, nxt and radium looks promising but like I said they are a lot riskier.
NXT and ARDR seem like a very good buy. Great dev and one of the best UI's and wallets ive seen along with a great system.