I just put three points per level into my Gadgeteer's Locks & Traps skill right from the start, and gave her a Thieves' Buckler (bonus to L&T) when I found one. Never had any real problems with locks or traps in the game.
I think I had another character cast Divine Trap a couple of times when my lockpicker was doubtful about some components of a trap, but other than that she did just fine on her own.
Keep in mind that the Locks & Traps skill depends on both Intelligence and Dexterity; if one or both of those is low, that will hurt your character's performance with locks and traps.
See the
"Rogue with dodgy lockpicking skills" thread for a recent discussion.