There is no simple answer to that question, but I think the most important point is to plan your investment in advance and research the potential of the coin in depth so that you can make the right decision. For the average investor, I'd say it's probably Ethereum or BNB or a top 10 coin at least and If you want to invest in an altcoin, but don't know where to start, a good place to look might be coins that have a low total valuation.