You could finish the Waffe Event without Paying / Grinding / Winning a single T55 game

The key part is: When you open a footlocker without getting a collection item, reopen it. It should not take no more than two reopening to get it from my experience.
The event lasts for 2 weeks / 14 days. You need 10 Engineer collection and 20 Harrier collection to finish it.
To finish the 10 Engineer collection:
You could get 1 Waffe ticket everyday if you win 5 randoms finishing top 10. And you could get extra 4 tickets as you progress on collections. That's 19 keys in total. Every winning gives you 1 footlocker and destroying 35 T55s gives you another 7 footlockers. It should be easy to finish the 10 engineering collections.
To finish the 20 Harrier collection:
You could get 1 harrier footlocker and 1 harrier collection everyday if you finish top 5 in dmg(without winning). This means that you could finish the 20 harrier collection in a 14 days span even without winning a single t55 game, if you play everyday. And if you were lucky enough to win one game or two, you could finish it sooner.
IMO the 3000 bonds is worth the minimal effort in this mode.