So here is a very basic Live Channel setup to try as a starting point :
Your Audio or Midi Source with it's Output Level ( 1rst available point of control & level adjustment )
The -Inf to + 0 Fader ( 2nd Level of control )
Utility Audio Effect ( you can use several instances per channel ) to trim or boost level, adjust the mono/stereo spread, write volume automation, panning.
vuMeter to check what level is sent to your Effect ( sweet spot is 0 dBvu = -18 dBFS )
your effect ( here a vintage comp. )
vuMeter to check what level is coming out of your Effect ( you want to get the effect only, not being fooled by louder sounds better ) so if your plugin doesn't have an adjustable output gain to trim/boost, you will need another utility to do that. The goal is to have the same level before & after your effect.
Adding some stereo spread with Imager
Using the channel Volume Fader as the last element ( it's a post fader ) to re-balance your track against the all mix. This has to be done several time when adding new tracks until the final Mix Down ).
On your MASTER Channel put a first instance of Voxengo Span with the K-14 preset first, then a first instance of Flux stereo Tools before your Mastering Chain ( Filtering EQ, M/S EQ, multiband compressor, compressor, limiter... Final EQ ) then a second instance of Span with the Full DBSF Preset and a second instance of Stereo tool to check the final Mix stereo image ).
This is one way to do it, I know it's somehow cumbersome, but the thing is that doing it for some time, you will start to find more comfortable to do it by ears, you'll learn about your plugins sweet spots & develop some muscle memory and in case of doubt you have tools to check the math & numbers behind what your 're listening to.
If you manage to have peaks around -10 dB but never exceeding - 6 dB and an average level around -14 or -12 dB Max and evenly balance each track in your Mix, you should be able to push it via your Master Chain and reach a "master" level around -3 dB and not sounding muddy.
The rest is about EQ and avoiding dueling frequencies, gate, side chain or LFO Tools for dynamic ducking, delays, reverb to create space & movement to the mix. When using virtual instruments, Midi notes velocity is also a key to bring live & humanize tracks.
All of this is just a canvas to play with, just trying to illustrate what I think is important to care about. The truth is that there's probably a shit load of ways to get a good sounding mix, but what I do believe in is : screw up your levels right from the start, and it's gonna be hard to get there 
So let's be clear, I'm not saying that you HAVE TO work that way, it's just about sharing what I think are good habits in audio.
OK, 'till the next track then !
