Which bands?
I recommend getting a pack of varying band thicknesses (see photo below). It's hard to give specifics here as different brands colour code differently. I recommend avoiding the tube-type bands with the handles, as they break easily and have poor versatility.
Essentially you want a light band that will be challenging for shoulder exercises (band pull aparts, face pulls etc), a medium band that will be challenging for pushing and pulling exercises, and a thick one for lower body exercises.
How to use them
Anytime you are using bands you need two points of contact:
1. An anchor point (to stop the band from snapping your eyeball out)
2. A free end to pull/push against
Once you have these two things, it's safe to use the bands. Below are some examples of exercises, showing the anchor (red) and free end (blue).
Recommended exercises are the band good morning, band row, band press, and band deadlift. Full video demos of these exercises can be found on my Instagram.
How to Progress
Honestly, it's much the same as you progress any other exercise. You can add weight, reps, sets, or add a pause. With the bands, you can also now increase the band tension by either choking down on the band a bit more, or adding a second band to the exercise.
In Strength,
Cill