devtrackers.gg
So I'm guessing this isn't possible to complete if you've completed the invade missions and still only WT2. Because until WT5 apparently you can't repeat them and run them, is that true?
Could you please elaborate on the OP question? Here are the ways to get more Apparel Keys for the Invasion Event:
Weekly Apparel Projects: three keys each
Chance to drop when reaching Field Proficiency upon each level after 30
Chance to drop when reaching Dark Zone Proficiency
Direct purchase with Premium Credits
As for the Invaded Missions, they reset on a weekly basis allowing you to replay them and face off against the Black Tusk more often and gear up to reach maximum Gear Score that much quicker.