my suggestion will be ada, str, rise, mana. but I am sure that there is many another altcoin that you can buy. I suggest you check one by one in the top twenty of coinmarketcap before you decide to buy the coins. you need to check how is the volume of each coin and it will increase in short term or not, how it looks like in the market, how is the trend of the coin and else. with doing this, I think you can find a good reason to choose the right coin for you.