Advice to practice dodging in the pantheons
Here is my genuine advice. Using the pet builds in the room you can fight bosses individually. I'm not kidding. They do damage for you, you focus purely on dodging the moves. This method in my opinion gets you through different phases while still practicing dodges really well. If you have any other advice feel free to share!
Edit: I know that it is also important to learn when openings are and how to attack during them. This is just advice so that people can first learn to dodge and get a feel for the boss, then I would recommend taking the pet charms off and only figuring out how to attack from there.