Makos

Argath and North part of Valley is same Tier.
The first five kill tasks you do (regardless of zone) will raise your skill.
It would be easier if you either do all argath task or all valley task to raise your skill.
but if you finish valley story task, you can request valley group task.
Once, you finished that, your next stop will be Sarith City. You should have 70 language skill by then.