Addons sadly are not really a thing. Or in some ways it might be a good thing. Completely not supported by SE. A few stand-alone programs exist (example, voice chat), but the useful ones that don't get you banned are few.
Macros you can search but personally I use almost none. Just the way the game is built is not as conducive to them as some other games. Still quite useful at times. Example: Black Mage ability "Aetherial Manipulation" teleports you to a party member's side. Well, if you want to go to a person, you want to buy cheap FFXIV Gil do it FAST or it's pretty useless. That's why you need a macro so that 1 button can say "target blah, cast Aetherial Manipulation". Also, macros are great for sending messages to party members. Other things you can do too, but they're mostly just "nice to have" rather than "set these up or you're not maxing your potential". As for where to buy FFXIV Gil and find a good reference... Dunno, your search is as good as mine.
As far as Addons go, SE plans to add in a Support for it, but no real date has been placed on it, or any details on the limits/Scope of the Add ons that we can make for it in the future.