Personally the first coin i really invested in was WAVES. After reading their white paper, some research, and being intrigued by their platform i decided to place about 70% of my total investment there. So far it has made me a good profit, about $3 per WAVE. I can see their platform going quite far with their decentralized exchange and their leased proof poof of stake system. As far as what the next big currency will be long term i don't know, im still pretty new to all of this crypto stuff, but WAVES Platform has my vote.

Edited: formatting, clarification.