Investing in top cryptocurrency aren't risk free as some coins falloff being at the top when the bull market comes and new tokens with new narrative are dominating the market. It's safe to invest in projects that are with the trending narrative and when the narrative is dropping you have to sell so you don't end up holding tokens that you can't sell as no individual is willing to buy them in the market. Some old projects don't have alot of profits left in them as new investors want new trending narrative.
To find new gem, I monitor new tokens that are launching on launchpad and monitor them to know if they'll be good investments. I also monitor the venture capitalist, that are investing into the project as the more money a project has the more they can promote the project and get their tokens listed on top exchanges that'll bring popularity and increase in trading volumes to the project which then give profits.