Congrats on a really good 8th grade track season. Even bigger congrats on being excited about the future and the process of putting in the work to get faster - hold onto it, the biggest gains to be had are in the long term and require consistent work. If you make sure you're enjoying the process, you'll keep putting in the work and reap the rewards.
As for this summer:
1. Run "a lot" - Don't stress about particular numbers, but make sure that your total training feels appropriately challenging yet sustainable. Try to avoid big jumps, but make incremental increases, like adding 5 minutes to a few of your runs in a week, then doing the same things a few weeks later.
2. If I were you, I would try to do 2 "workouts" per week, but keep these different in nature from what you would do in-season. Keep the intensity lower. You will have a full XC season of racing and workouts that are in the neighborhood of race-pace. Use the offseason to touch on paces and effort levels that benefit your fitness, but you are less likely to hit during the season. Tempo runs/reps are great. So are progression runs or fartleks where the offs aren't particularly slow.
3. Work on your neuro-muscular strength/activation/speed/mechanics. Find a routine of drills that you like, and do them a couple times per week. Find a core/resistance routine that you like, and do it once or twice per week. Do some very short, all-out, alactic (no lactic acid buildup) flat sprints like Flying 30's and steep 8-10 second hill sprints with full recovery. In fact, a set of 4-6 of each of those within every 2 week period would be great.