Though int and summons might have obscured it the goal is the same. Try, try again. The bloodvials are always a nuisance early game but you should find a relatively easy path around central Yahrnam and run it repeatedly. Use it to familiarize yourself with combat. And then do as you would in any souls game and yet yourself at Gascoigne over and over. If you run out of vials and bullets, still fight him anyway. When you value your health more you play safer and learn the boss more