Halo Wars 2

This achievement can be earned over any and all matches of Blitz, be it online or in the Firefight Mode. Generally, it should come naturally to those who are actively playing Blitz. Depending on the opposition, the cards you draw, and your Energy level, you can play anywhere from 30 to 60+ cards a match.

If you desire to get this quickly, though, it's recommended to fill your preferred deck with cheap (low Energy) cards and spam them as often as possible while in a solo Firefight match against the AI (don't do this online as it'll just disrespect your teammates). If you focus on seeking out Energy Pods and playing cheap cards, you should be able to play a decent amount before the match ends due to the AI capturing more zones than yourself.