if I think personally a safe way to invest in cryptocurrency is :
4. invest in project that are in the top 1-500 in coinmarketpcap (have a high volume);.
As usual we must invest on the projects that is in the top of all the rankings so we must invest first in the first top 10 projects or coins in thre coinmarket cap, not in the top 500 coins because with this wide range there is a lot of trash coins and projects ranging 100-500 so it is not precise to invest in this kind lf projects. The rank that we must invest into is the top 10 or the most good and awesome projects and coins that are listed in the coin marketcap because I believe that this are enough evidence that they are legit.