Tips for playing HRE?

I'm kind of new to CK2, I did sort of well as the bastard, I got the empire of francia, I didn't do much with ireland, but I did get a kingdom out of the crusades and I was working at spain, I guess I had gavelkind succession? And then the HRE invaded.

Now I'm trying to play as HRE. I'm trying to get medium crown authority, but I don't do very well when the revolt starts. How can I play HRE better?

Thanks