Perhaps I've always been a lone ranger, which sometimes makes me feel lonely. I'd like to connect with cryptocurrency investors from around the world and share our insights and experiences.
Just buy coins that many people have bought it. Don't isolate yourself by buying altcoins that don't have prospects. Just buy coins that are certain to profit even a few, rather than expecting big profits but full of uncertainty or tend to lose. I've been in your position where bought altcoins that don't have fundamentals but expected the price to increase many times over, where in reality, the prices fell like a waterfall on next month.
A lot of people bought SHIB and DOGE. Does that mean he will as well follow it? I think that was a wrong strategy. Just because many people have bought it does not mean it is already a good coin. What we need to be successful here is not instincts or luck but it is knowledge.
The OP didn't say that he was once an enthusiast of pump and dump coins but I think he is not only updated with cryptos, and that is why he is asking for a good recommendation here. When he say mainstream coins, I believe he is referring to the fiat or on what we can see in the forex market. They are still useful and you can still make a profit out of them but altcoins has it's own advantages as well. Balancing is only the key here.