Based from purely my experience, I would say that participating into campaign signatures and HODLing are the best ways of earning cryptocurrencies.
As someone who has been active in this forum since 2017, I have participated already in dozens of campaign signatures during my stay. Throughout those 5 years of experience, I have accumulated at least a handful amount of BTCs where I avoid spending/using them and HODL them for long-term. Given also that the nature of campaign signatures makes you work at your convenience, it is not time-consuming as it is definitely a privilege to participate in such.
HODLing will also remain as the best way of earning cryptocurrencies since you take advantage of BTC's inflationary value and limited supply in the market.