Strongly based on hexomino's answer, I think you are a
Phone
With two, I’m active
on (in the state of being active, functioning or operating)
With three I’m first or second
one (according to zero-based numbering, the element in position one is the second element rather than one-based numbering, where the element in position one is the first element)
With four, I set an example
hone (a sharpening stone used for removing the burr from the blade of a razor, thus setting an example that all razors should follow if you want to cut more accurately)
With all five, I work backstage
phone (a phone has most ─ if not all ─ of its processing inside, that is, in its "backstage").
Hint #1:
The usage of the word backstage may not imply its absolute literal meaning.
Backstage is not used literally here, since backstage means situated in the area behind a stage.
Hint #2:
I may do good if you use me, but bad if I use you.
I think it's something related to the idea of this article.