Macros

So I'm a complete noob with windower macros... Is there a way to equip a certain armor piece for if one avatar is out without having to write a seperate macro just for that avatar? Like ZNM Head piece for Garuda during Physical Blood Pacts or Fenrir's Crown for Fenrir?

Only spellcast can do that, which uses rules you set for it to know which piece to use for what.

Like if garuda= /equip karura hachigane etc

I don't use Windower macros or Spellcast. Here's how I addressed the problem:

Macro sets. I have one macro set for spirits, one for idle, and one for each avatar. My Release macro (Ctrl+0 on every set) sends me back to my idle macro set, which has my macros for summoning various avatars. Ctrl+1 on every set is resummon current avatar (on idle set that's my Carbuncle macro since he doesn't have his own macro set). The various summon macros on my main set, after starting the cast, change to the correct macro set for that avatar.

Then it's just a matter of customizing each set for each avatar. For example, Alt+8 is my perp down equipment on each macro set. For Garuda, Alt+8 puts me in Vayu's Staff +2, but on most other macro sets Alt+8 puts me in Bahamut's Staff since I haven't done many of the perp staff trials yet. You could do the same thing with Karura Hachigane.

This also makes it easy to memorize macro slots, for example Alt+4 is always the avatar's strongest magic BP, and Alt+5 is the avatar's strongest physical BP. Alt+1 is always Assault. Alt+6 and Alt+7 are wards of various kinds.

Also, you can take this a step further! On my idle set that has all my summon macros, I set up the macros in the order of the elemental days of the week. So Ctrl+1 is Carby, Ctrl+2 is Fenrir, 3 is Ifrit, 4 is Titan, 5 is Leviathan, 6 is Garuda, 7 is Shiva, 8 is Ramuh, 9 is Diabolos. On my spirit macro set, they're in the same order too based on element. This has helped me in a lot of ways, in particular to know the order of the days of the week in Vana'diel.

Smart macro design impacts SMN a lot more than most jobs, I think.