My gf love anal I love to fuck her ass and we do use toys as well. What else I can do to her to give her the best pleasure with anal?

Fuck her ass, eat her ass, finger her ass, dildo her ass, plug her ass. Do it often and keep up a routine with it, and it’ll just keep getting better. Find what you both enjoy a lot and keep doing it. If she wants to keep pushing her limits, work up to larger toys and give her a stretch. It all kind of depends what you’re both into.