As you can see bitcoin dominance is rising, so I would just buy bitcoin. Don't forget that the lightning network is coming, and this will probably make a lot of alts obsolete. Most of the coins just invest in privacy protocols, that are important but are not the main issue that needs to be fixed. Bitcoin is solving the scalability issues, and it will be able to compete with payments methods like visa. It kind of already does, in my opinion, but it will get really good at it. My bet is bitcoin, but if you really want alts, I would probably by stellar or ethererum. Litecoin will always rise as well, because it does whatever bitcoin does, and it's not really going away either.