The frequency of your workouts depends on how good your diet is and how much sleep you get. And for plyometric work, try doing exercises for time such as tha tabata protocol

IE: jumping lunges for 20 sec/rest 10 sec
jump knee tucks for 20 sec/ rest 10 sec

goal is to do as many as you can with good form in the 20 sec then rest and repeat

Put exercises together and go thru the circuit atleast twice and then gradually work ur way up to 4 circuit repetitions

Mix up exercises everyday though to keep challengin your body

I didn't really get back into doing plyo's until a few weeks ago, but I've been doing box jumps and have been loving them.

Size of the box will obviously be determined by what you have access to, I would mix up between doing sets of jumps for reps and doing jumps for time.

I personally am only doing them once a week, but you could probably get away with mixing one plyo exercise in with your workouts just about every day since you've already got a good base.