UO Second Age

does detect hidden need to be gm or is there a level like 70 or so that works just fine for
virtually any situation you would find during gameplay

If you want to detect people with 0 hiding using the invisibility spell(or items), then 50 is enough to have a reasonable chance at revealing them. If you hope to detect anyone with any decent amount of hiding, then you absolutely need gm.

actually im looking to detect traps on chests and such

how much do i need to reliably do that?

50.1 gives you the chance to "area" detect traps, or even determine if they are trapped, but the range is rather small. Also, you only have a 25% chance or so of even detecting any. At GM you detect the whole screen with a fairly good (95% or so) or picking up the traps, also some traps (dungeon traps ect..) become visible to you that would be otherwise hidden. If you arent trying to reveal people, I would say that 80 should be okay, as long as you use the skill twice to be sure you caught everything.