If you are starting the game from scratch and trying to get every achievement, it is most efficient to go for this achievement in the Chinese heavy tank tree. This is because
requires you to research a Tier 7 tank, which no other nation requires for their achievements. Because you are already at Tier 7, you should continue on this same path to unlock this achievement, which will be a long, long grind (at least 100 hours, with a premium account).
If you are only
going for this achievement, there may be cheaper/faster paths to unlock this other than the Chinese heavy tank path, but none more efficient for stacking with other achievements.
Note: Some people have reported that they personally don't like the later Chinese tanks and therefore are not as good with them, and as a result do not get as much experience per match. In theory, if this is true for you, it may be worth (i.e. more efficient) going with a different country's tank tree if you find yourself really playing poorly with the Chinese tanks. Unfortunately it takes quite a bit of investment to unlock the tanks to the point of deciding if you like it or not, so it probably just makes more sense to begrudgingly grind through the final tiers instead of experimenting with other tank trees to see what you like.