The best way to make money?

I mean, how i can get fast mesos

And that's what he meant.
Mobs you can train on don't drop anything valuable.
If you want to make meso you have to spend a lot of time (or real-world money, but I assume that's not what you mean) doing things like crafting and merching.
"fast meso" is not possible, for the simple economic reason that if there was a way to make a lot of meso easily, everyone would use it, and meso would become even more worthless than they already are.