I use a variety of ways to track my crypto portfolio, including using the built-in tools from CoinMarketCap and CoinGecko. I tend to find the latter a bit more accurate since it includes the transaction fee in your total returns, whereas CoinMarketCap does not.
Separately, I keep track (and ensure the accuracy of the online portfolios) using Excel. I recently created my own Excel spreadsheet tracker which I intend to share in the near future once I have all the features built. It's quite a low maintenance tracker and all I need to do is enter my transactions manually (e.g., buy or sell) and the spreadsheet handles all the updating and tracking for me, including calculating my gains and losses versus the market price. This is accomplished by accessing the CoinMarketCap API (free for personal use).
There's an excellent HOWTO guide on linking the API to Excel here.
How do you track your portfolio? Let me know in the comments below.