I'd strongly advise you to do a lot of due research into alt coins you might be considering. Don't invest purely from looking at the market cap and picking one in the top 10 or something.
Keep in mind there are not many actively used and functioning blockchains, many are still just ideas or still being built and awaiting testing.
How long term are you talking about 1-2 years? or much much more?

NEO will be mentioned a lot, it is a very nice project with tons of potential. Be cautious though with it, it's completely in bed with Beijing, it's how it survived the chaos with ICO and exchange closures. If they fall out of favour with Beijing it's down the toilet big time.