Hi Random.
You say that you have been picking for 5 weeks and have mastered a couple of locks then got stuck.
Picking is not a linear progression. Just because you have picked one brand of lock does not mean they you have mastered all that brand or model. Every lock is different. Some Masters are easy but others can be very difficult.
Practice on as many different locks as you can get your hands on, even locks of the same brand. Some Chinese locks can be very difficult because of sloppy manufacture others because they are well made.
You have to develop a “feel” and that only comes with practice. Try using different picks to get locks that you have already opened. Try using TOK and BOK torsion etc. Look for locks with difficult bitting.
Get as many locks as you can and open them over and over. Trying to “hear” what the lock is telling you and develop that feel.
The only sure way to master this skill is practice.
If you find that you are getting frustrated with one lock. Put it away for a week or so then come back to it.
Remember, there will always be locks that you won’t be able open for quite some time (if ever).
All of us here have a “Naughty box” that have real beasts in them.
The suggestion to get some 140s is a good one. They are cheap and will teach you a lot. Each one will have its own character and will teach you something.
Happy picking.