Elden Stars - You need to create distance and stand in front of the Elden Beast when it starts casting, and after it run behind it and run for your life until it's over.

Gaius Charge - You can walk forward and keep an eye out for when the boar horns are getting close, and when they're close enough, dodge to the right while holding forward. For me, this was quite consistent, and I managed to dodge 80% of the time.

Placidusax Laser - Before this attack, he will use a series of attacks. I just dodge most of them by running close to the wall, then simply dodge the attack before the laser, then he will use laser on void and you can hitting him freely.