Step 1
Buy GTA V and Witcher 3
Step 2
Now you have (at least) 500 hours of gaming (100 hours GTA V SP + 200 hours Witcher 3 + 200 hours GTA V Online). Play what you have.
Step 3
If 500 hours wasn't enough then play GTA V for a few more hours.
Step 4
Summer ends, if you have done everything as i said you should have had a wonderful summer.