I've seen a couple addons that do something similar to what I'd be aiming for, but haven't yet found one that actually works for what I'd like... so I figured I'd try making one myself.
What I'd like to do is make an addon that can add an overlay symbol of some sort to items with certain purposes, such as Artifact Power or Reputation. I tend to use the Legion Companion app a lot and sometimes log in to find so many AP and rep items that it fills up my bags and mailbox. I'd like to be able to highlight the items that grant AP or rep, so I can make sure I don't miss anything. Further, I might like a sort of macro button I can add to an action bar or similar that will allow me to use each of the items in my inventory. I know there's an addon for this for AP items, that puts a large button in the middle of your screen with one of the AP items in your bags, and each time one is used, the button changes to the next AP item in your bags until they're all gone. I'd like to have this option for rep items too, but perhaps in a more customizable interface, like a small window or an action bar button that cycles through each item one at a time until they're all used.
My issue is... while I know the basics of making an addon, I'm not really sure the best way to isolate rep and AP items, or how to modify the graphics in the interface where those items appear (such as in the inventory or mailbox). I could probably try to skim through code of similar addons and adapt it to my own uses, but I think it would be better served to ask for help finding the answers for myself. Are there good tutorials, or guides for this sort of thing? Are there members here that could help me understand what kind of code is needed, or even help co-author the addon to make sure it works? I'd appreciate any help that could be offered.