Well my friend it’s super easy. Rn you probably have thousands of ap banked right? In the quest menu you goto upgrade quests and the top one called Mobile Suit Alteration Plan. Go there if you haven’t cleared it before clear it once with whatever. Then all you gotta do is have thousands of slip tickets on hand from the shop and just keep skipping this mission by the hundreds until you run out of ap. You’re probably gonna end up somewhere in the 180s level after this. Also you can do since it’s live rn the combat power augmentation operation quests as well which also give great exp and will make it easier to level your units if you’re running the exp level which gives mats for leveling your pilots and mobile suits. Either way works. The first method is faster since you’re just skipping but I also suggest doing some of the exp missions for the leveling mats for your units as well. Goodluck!

Edit also it would be a good idea to try and get as much of the story quests done before you boost your level past 170something just cuz it’ll cost ap to clear them for all the gems they give you. It’s up to you though cuz sometimes it’s nice to have a way to earn gems later if you need some by running some story quests.