To earn this achievement you will need to purchase all of the Weapon Skills, Core Skills, and Augments for one vocation on either you or your main pawn. To do this you will need to reach the maximum rank for a vocation and also have lots of discipline points.
I recommend you earn this by purchasing the skills for your pawns vocation. This will leave you room to change your own vocation without worrying about spending discipline. The Sorcerer takes a lot more discipline for this achievement than the other classes. The vocation that costs the least discipline is the fighter, and the advanced vocation that costs the least is the warrior. Choose one of these for your pawn and you should be able to get the achievement before the end of your first playthrough. You could easily get this with another class, but it will take a bit more time. Your discipline points will carry over to NG+.
You can save before purchasing the skills and reload after purchasing to keep your discipline points for trying another vocation. The achievement will unlock as soon as the lost skill is purchased.