If one’s going to argue about choice of first programs, a proper Hello World on classic macOS requires the use of the Mac Toolbox. Using the bundled Think C console isn’t really producing a Mac-native program.
Vintage Macintosh Programming Book Library - https://vintageapple.org/macprogramming/
https://developer.apple.com/library/archive/documentation/ma...
https://developer.apple.com/library/archive/documentation/ma...
For a more directed and more C-oriented walkthrough, the Macintosh C Programming Primer was a pretty common go-to. It's been out of print for ages, of course, but there's a PDF available at:
https://vintageapple.org/macprogramming/pdf/Macintosh_C_Prog...