How Often?

When I visit boxes I notice that a class typically consists of a warm up, working one skill then doing a WOD.  With so many different movements to learn ( Handstand pushups, snatch, front squat, muscle up, handstand walking) you maybe get to work drills etc for any movement once every couple weeks, and if you miss that class you are out of luck. 

Like anything, you must put the time into getting some skills.  If you are going to class and using it to get in shape that is fantastic!  If you have hopes of getting muscle ups, hspu or snatching heavy weight etc, you will probably need to work on those outside of a normal class. 

I have had people that were not strong enough in dip or swings try muscle ups.  They took the time three days a week to work ring dips, swings, pull ups, and assisted muscle ups.  It would take them an extra 10-15 minutes, and you know what?  They got their muscle up, but they put in the work.

You are not going to instantly get any new skill, follow the tutorials and continue to work the drills - you will get better!