In a typical game, the first outdoor area that I clear is Kriegspire - after spawning all the drakes (sometimes I just kill the drakes and leave the rest for later). I usually try to get master learning right before I do that as the extra experience I get from that seems to make it worthwhile. And of course I always have a Teacher and Instructor in my party when I'm clearing areas for exp.
By the way, clearing those drakes is almost always the 'breaking point' in my games. It gets me both enough exp to master most everything I really need and enough gold to not have to worry about that anymore.
Some of us have done high level games and in that case it's of course worth it to put a lot more points into learning beyond master. But for a normal game I think just getting master is sufficient.