Sound Combinations
I've be experimenting with some registrations (sounds combinations), but it's not just the sounds themselves which can be layered, it's the type of effect that can be added to the overall sound.
Reverb can turn a flat sound into a big sound, but don't over do it, also think would the instruments I'm using benefit from a small or large amount of reverb?
Another effect I use is Chorus that can create a bigger sound.
For guitar sounds I've been using some delay, but working on the other effects.
If you use styles revoice the sounds, mute some of the tracks to create a less busy style, better still try without any style.