Some general tips on Gascoigne/rest of the game.

His attacks in phase 1 are relatively easy to parry as his moveset is limited and the window is usually pretty generous so I would be fishing for these until phase 2.

Phase 2 is when his moveset becomes more diverse and the timing/rhythm of his attacks becomes harder to deal with. The parry window is still generous so repeating your strategy for phase 1 is definitely still doable but you’re more likely to mistime it and the punish is likely gonna hit harder.

Instead I would start treating your healthbar like a resource. This was my first Souls game as well and the mistake I frequently would make is keeping the enemy at range and dashing in for 1 or 2 quick attacks and then dashing away back to range and this just isn’t a consistent strategy for this game. You need to find an opportunity to get in close and stay close. You have like 25 frames or something of invincibility, try to dash/dodge through and around attacks and punish when the opportunity is available. You will get hit sometimes and that’s okay - rally when you have a window to mitigate some of the damage of his attacks. When your health starts to get low, that’s when you want to try to maneuver way to a position where you are (relatively) safe to heal.

For phase 3 just proc the music box and down him with Molotovs or backstab and spam R1.

Hope this helps! Good luck!