im kinda stuck ?
You can’t level masteries through WvW. My advice is start the HoT story, go into the new zone and find a quest chain. These happen around outposts. Try to stay with groups of people and follow along through the quest chain. Yes, your XP booster will help, along with food and utility boosts.
It might also help you to join a friendly guild who you can play with, instead of trying to solo what is a pretty hard area.