regarding playing with a band.
1) you can't improvise as well if you don't know the underlying chord progression. So you really should focus on learning them however you do it. Mainly I focus on what "mode" is this chord progression? Is this minor or Dorian? So you don't make the mistake of hitting that natural 6 when it should be sharped. Is this mrjor of mixolydian? Best way to know this is to apply the chord scale to the chords being played over and figure out where your tonic is. A good rule of thumb is if the tonic is minor and the IV is major, you are really playing Dorian. That's just how I look at it though.
2) it's going to be much easier to improvise if you already know some songs of that same genre of music to use as a "template". If the backing music is a lot of I-IV-V's find guitarists you like that are playing over those and learn some of their licks. The point here is to build up your "Phrasing". What notes does (your favorite guitar player here) end his licks on mostly? How does that note make you feel (resolved or tense?). And incorporate that into your soloing. I find that I like to start licks on the 1st, 5th, or 7th scale degree, and end licks on the 2nd, 4th, dorian 6th (when playing dorian). This is useful for creating tension. When you start a lick on the root and end on the root, 3rd, or 5th every time your solos can become very bland, and not seem to move around enough to be interesting. That's not to say you should use this as comprehensive list of how to play. Blues solos land on the 3rd scale degree frequently and it's a poweful note when not overused.
3) practice building solos, and notating solo structure by other people. Improv is great but 3 minutes of licks can be tiring for anyone listening. Listen to some of your favorite solos. Make notes on paper (or notepad.exe) of 3 or 4 solos. Write down things like:
measures 1-4 slow melodic notes, low on the neck starting on 1st, ending on 3rd
measures 5-8 same melody but an octave higher
measures 9-10 fast legato lick starting on 3rd ending on 6th
measures 11-12 hendrix style bends and pull offs in minor pent shape
etc..
this will give you a good mental template of what to do when you play so you arent' just playing scales for 3 minutes. This is what I do but I'm an amateur and I play mostly improv. Hope this helps buddy.