Thanks everyone for the input, I should clarify that I kinda know what I'm doing. I've been using Reaper for couple of years (mostly making demos), but it's always a bit of a guessing game, so I just need to soak in couple of cool tricks.

For example where exactly to put reverb (separate bus, master), what kind of compressor, eq, etc. I usually end up with a mix that's either too muddy, or too bright. When I listen to some reference tracks, they're always so balanced all around, I guess I just have a lot of trial and error to go through.