Hi.:)
As in every single kind of special action(others include stealing, monstalogy, digging, even building), you don't start off as a pro, with the greatest success guaranteed. With robbing this is even more so, it will take a very long time till you can get real good. Two important issues:
-The most influential factor naturally is your robbing skill level. Your "attack power" against any trap is raised when you level it up.
-Attributes are more complicated. Persistence helps against one specific trap, dexterity helps against another. The higher the appropriate attribute point is, the easier it is to beat a given trap BUT the lower exp that trap will wield.
For a successful robbery though, level 1, with robbing skill:1 is enough. Your chances will gradually get better. At first, stick to the dark district(till about robbing level 80), try around the casinos.