I love making Judy patterns! I've made about a dozen of her patterns. I was very intimidated at first until someone showed me how to get started with organizing. I started with Island Sunrise. Simple spikes and curves. You absolutely can make her patterns without a class. Only the ones released every 2 years, called Technique of the Month, are available from certified shops or instructors.
There is also a program called Quiltster, designed by Quiltworx, that you can pick a Judy Niemeyer pattern and color it using the many thousands of fabrics available in the program. There is also a way to upload your fabrics so you can use your stash. Then you will have a picture of what it will look like before you even start. It will tell you fabric yardage. too. There is a monthly or yearly cost but worth it if you make a lot of her patterns or just want to try it out for a month. There are videos to help you learn to use it.
I am a very organized person. I am a directions/recipe/pattern/rule follower. I have a hard time using that other side of my brain. You know, the creative side. I have a friend who is the total opposite of me. She just figures out how to make them work for her. Hers end up just as beautiful as mine. It doesn't matter how you get there. Have fun!