If you're interested in a long-term strategy, I'd suggest you a very simple conservative strategy:
1. Split your investment into top10 coins by market cap. You get lower risk and average profit.
2. Rebalance your portfolio once in a month.
3. Enjoy
This is a good strategy also. It is not necessary that it should be the top 10 coins in coinmarketcap but what coins does he think have a future base on the projects, roadmap and developers. He can do his own due diligence and check the fundamentals behind each coin. He can do dollar cost averaging wherein he will buy a coin monthly or bi-monthly and then rebalance.