Get your squat up!- is my advice, increasing my weight in this lift has helped me improve a lot. Try and get to 1.5x bodyweight.
Also, because you're just starting again, a good idea (IMO) is to go out to the courts/track and spend 10-15mins once or twice a week just practicing your SVJ and 1 and 2foot RVJs. I found that when I decided to get back into it, my technique was gone and just getting out and practicing the entire jump - run-up, plant, arm swing - helps a lot. Look around the site for more advanced stuff like plyo workouts etc. for speed/reactivity.
Good luck!