The below is my opinion only and NOT financial advice!
If you are in it for the long term and won't sell for years, I think the best thing to do is invest in coins that are like successful blue chip stock.
Think about Microsoft, Amazon, Google, Walmart, McDonalds, Procter and Gamble. All of these stocks are important in our economy.
For crypto, think what is also important:
Cryptos that are actually used by other cryptos (many cryptos needs other cryptos just to work)
Solid use case
Credible development team (do you trust them?)
High rate of development on Github
Already high market cap (coins or DeFi tokens in the top 30).
Some examples of coins/tokens that meet most if not all of these criteria are ADA, GRT, LINK, UNI. In my opinion,
But don't listen to me, as always said DYOR (do your own research).