If you are going to work in Tier 1, you build your app using the AppGameKit IDE in a Windows environment.
You use Xcode to build the Mac (and iOS) versions once you are ready to test on the actual device and not through a Player (which you usually need to build yourself for iOS and Mac).
And, you will need an Apple Mac Developer's License ($99/year) to publish with Apple. I know you need an iOS Developer's License before you can start testing on devices. But you might not need that Mac License until you are ready to try publishing.
There is an official
AGK guide for Mac Publishing (which covers the basics).
However, it gives totally incorrect information about copying the Players\Mac folder. Since that folder contains only a text file which is useless. They haven't updated the guides since the first release.
The guide doesn't talk about copying the interpreter_mac directory and renaming it and I think it is a bad idea to keep reusing the interpreter_mac directory as appears to be implied by the rest of the guide. By copying it fresh for each project, you don't have to worry about deleting old media or which app version the bytecode.byc file is.
I just update my iOS Tier 1 instructions for Mac and will create a post in this forum with the instructions.
If they are not clear or you have issues, please let me know.
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master