I strongly recommend you to buy NEM and keep it for longer term then you will earn more money than other coins.I expect this coin will hit $10 by end of 2018 and also has great potential in the future.The current price of NEM is $1.12 and I think it is an affordable coin for you.
If you are looking for a coin with short term investment then go with Ripple but I can't see any future for this coin but still the price of ripple keeps increasing so you have chance to earn good money in short period of time.