Well, you need to move fast to move fast so you might not see much improvement unless you used plyos for a couple weeks before testing your vertical.
I think CT wrote about doing plyos for six weeks leading into a season and then cutting them out.
For volume and loading I aim for 60-80 contacts for beginners. A contact is each time a foot touches the ground. Jump up and land = 1 contact. I do 80-100 contacts after the beginner stage and top out at 100-120.
These numbers are per session and I only do two a week. I also start with less intense stuff and progress from there.