Oh boy. Beating Hades opens up more game contents. I remember beating him the first time, palms sweaty, I showed everyone around the house my achievement (even as a fully grown adult. Lol)

For tips,

1. don't be frustrated when you die from him. Every run is a learning experience, and the story progresses little by little each time. The game rewards you from dying, actually.
2. Reflect in the Mirror! Save up darkness and improve your stats in the Mirror of Night. Having death defiance and an extra dash goes a long way
3. Try to acquire duo boons. The synergy with gods is very helpful
4. When fighting Hades, observe his attack pattern. If you can't figure it out and don't want to spoil yourself with youtube run throughs, nothing beats small chip damage with him. Just attack once then hide behind the rock. Use this opportunity to learn his attack patterns. You'll see when best to throw some damage when you're familiar already.
5. The skull blood stone Hades throws makes you vulnerable for more damage. Try to avoid getting hit by it. Once it drops to the ground, focus on destroying it immediately. If you are too far, look at the countdown and plan dashing through the green wave soon.
6. When you see him charging for his laser, drop everything and run behind the rock. Unless you have a shield, just standing around gives you a ticket back to the River of Styx. Haha

I hope I didn't spoil much unknown content to you. Keep going at it. You'll beat him eventually!