visit coinmarketcap, and see top 10 altcoin, now you can go to the market and buy some coin refernce from marketcap, because that's a major cryptocurrency in crypto world and great future
Major coin might be good choice to invest because it's very good in term of marketcap. However it's better you look at the chart of each tokens. From those perspective, you can choose which one is better and suit you. Since the need is different from person to person, you may choose the fastest one or the slower one based on their movements.
If I personally really like picking coins that are in the top 5-10 in coinmarketcap,
we can buy a coin that now serve as the order to invest for short term or long term investment.