On my blog I have some details on investing outside of crypto. I will eventually update the page with more details on my exact holdings. Generally I go with an ETF split that indexes these markets:
50% US Total Market, 40% World Markets, 10% Emerging Markets.The general rule is 100 minus your age is the percentage of your portfolio that should consist of stocks.. so if you were 25 you would hold 75% stocks and 25% bonds. The sub portfolio for crypto is mostly personal preference and risk tolerance.
The amount of different types of coins an investor purchases is again personal preference. There is nothing wrong with a portfolio's crypto portion being 100% bitcoin - and it might actually perform better than one that has a lot of alt-coins that under-perform/lose value...
A lot of people in this space are looking for "the next Ethereum" and invest in the newest flavor of the month coin without doing any real research. It also takes a lot of time managing the private keys and wallets for each coin holding.