Lockpick is actually worth putting one point into at about level 12, then at the Bandit Camp...
Killing the bandit leader Jagon gives you a +1 Lockpick amulet.
Use that to open the level 2 lock on
the top floor of the Black Boar inn, and picking up the book there, which will eventually lead to you finding a Skillbook.
If you don't mind doing a LOT OF backtracking, you can wait until Sentinel Island - but BEFORE entering the Battle Tower - to fully max out Lockpick. The stuff you'll find in the chests is scaled to your level, so you'll get a lot of good stuff at level 15, instead of less good stuff at level 5.
If you hate backtracking, put points into it as you need it. But definitely, max it out, there are lots of skill points and locked chests.
