Yeah I can help with this, since I actually beat Gomess doing exactly the same thing. I didn't even use bottles except the single one that is required to complete the game.
Your biggest problem is running out of magic power. Light Arrows are necessary to beat him but they use up 4 MP if I recall, making them costly. Without Green Potions or at least a doubled Magic Meter you're in trouble. What you're going to have to do is block 90% of the time, and only attack when you've got a clear opening. Using your shield perpetually. When you have the opportunity, slash his body with your sword to kills bats. Sometimes they drop Magic Bottles, or possibly even Hearts (I don't recall for sure on the hearts though). You can use the normal bow to kill the bats for items too, but you also don't want to run out of arrows, so the sword is better.
Play defensively and continually replenish your magic. You can also use the crates in the corners as a few of them have hearts, though not many. Good luck, and if you still can't do it tell me exactly where the problem is and I'll see if I can help more.