Recently, I have been recommending the index fund approach more and more to my friends.
One of the most notable people in crypto, Naval Ravikant, said in an interview how his exposure to crypto is through a fund. He also oversees the Bitwise HOLD 10 https://www.bitwiseinvestments.com/.
The fund holds the top 10 cryptocurrencies by market capitalization. I like this fund because you can purchase it with fiat.
If you are an accredited investor from the US, that is a great option for you.
For us normal people, it is more reasonable to use a tokenized fund such as Crypto 20 (C20).
https://crypto20.com/en/
You can get C20 tokens at exchanges such as HitBTC and BiBox.
The Crypto 20 fund holds the top 20 cryptocurrencies by market capitalization. It is a closed-end fund so you will have to pay a premium for the tokens relative to the NAV (net asset value). Also, you can liquidate the fund directly on the website for Ethereum. However, your wallet address needs to be registered with the tokens in them on the website and US residents are blocked due to potential SEC regulations.
Regardless, you will be able to sell C20 tokens on exchanges and the NAV being backed by the equivalent dollar value in Ethereum prevents its price going below the NAV. So, it makes sense to sell the tokens back on exchanges for the premium price when cashing out.
In summary, for the rich people get https://www.bitwiseinvestments.com/ and for the regular people like me https://crypto20.com/en/. I believe this is a better way to manage your crypto portfolio since you do not have to hold the crypto yourself to get exposure and you only get charged a small annual expense ratio (0.5% for crypto 20). It is the best buy for those who do not have a lot of time to research cryptocurrency and want a 
passive investment.