The area is comparative to the skill level

An important thing to know about Lock-picking is that skill-ups from locked doors are on timers in the game Blade and Soul. You can only gain a skill-up once then you need to wait 20 minutes to get the blade soul gold next one. There are ways to get around this though.
One way is to successfully pick a junk-box/practice lock in between attempts. Another is to pickpocket a target, which has a 50% chance of resetting the timer. You can make an effort to collect junk-boxes/practice locks and then head to a door and go nuts practicing though pick-pocketing is blade & soul gold the better solution.

The alternative is to simply stand in town and tell people you will pick their lockboxes for free. The lockbox can be in the do-not-trade window and you will still gain skill. Problem is, you need to be on at peak times and most servers are very laggy during these times, making it very frustrating. The only time this really doesn’t work is when there are additional casters around as they can really put a dent in your hit points.