I believe BRD lost its access to CNJ skills in exchange for PGL.

My advice is to play on your main class, but spend some time in the other classes to get any abilities that appeal to you. Once you hit level 30 the job quest will show up and they will tell you what sub-class you need leveled.

Leveling the sub-class will be much faster if you do it this way, as now there is a system in place where classes level up faster if they are not your highest leveled class.