For many gigs - especially those where I'm using only a handful of presets - I'm using FM3 plus 2 external buttons and one expression pedal. The external buttons' main functions are to (i) increment the view so the 3 buttons of the FM3 scroll through up to 4 views, giving me 12 primary and 12 secondary (hold) functions per layout, and (ii) tuner/mute. The primary tap functions are mostly for scene selection (a combination of toggling and incrementing), for FX block bypass, and for solo boosts. I use hold functions within presets to change to other presets, and on FX bypass buttons the hold function often increments channels within the FX block (especially for delays). The expression pedal variously controls wah, gain level, delay time, delay feedback, volume swell, depending on the particular scene/preset.
Being able to readily scroll views has been key to using just the FM3, and since I've been doing it this way there are fewer circumstances where I use my big board (which has an FC6, 4 expression controllers (2 full, 2 micro), and a ton of external switches).