@Christine Thomas
From someone who have self tough himself I can advise you what are the first step you should take, and how to save some money.
First Step:
Learn the tool "Grasshopper", if you don't know the basics you will not manage to make any advance in any direction.
For this step I advise you to follow the steps I have posted to someone in your same situation in reddit.
https://www.reddit.com/r/rhino/comments/eagr2l/learning_grasshopper/farwv62/
Second step:
Just watch ArchiCAD youtube videos for Grasshopper, I know they are few, but for starts, there is nothing more in it, the rest is based on you knowledge of Grasshopper usage and your already known ways using ArchiCAD adapted to Grasshopper's graphical user interface.
A good friend of mine have once told me that I´m so brute that I´m capable of creating a GDL script capable of creating GDLs.