If you're talking about a strict PvE build for your character, it's not that you'll mess up a build. You'll more likely paint yourself into a corner by dedicated leveling up of one stat and then, when getting to a boss, find that you put too many points into something when you should have been getting a bit more of another thing.
I wouldn't worry too much if you had problems with Bell Tower Gargoyles. It sounds like you're new and are getting used to Dark Souls and how it plays. Just continue to level up what you think works. I could tell you what would work for your character and what stats you might want to focus on, but you're more interested in playing the game without guides, it seems.
Continue to level up what you think you'll need. The game is harsh and will teach you what you need at certain times. Don't feel bad about going to a safe place next to a bonfire and grinding out souls against enemies that are easier for you. You'll find a few places in the game are useful for this (Forest after the gate, Anor Londo Silver Knights) to get the souls you need for a few levels in something to even you out. While the game is harsh, it is fair and won't make it impossible for you to continue on. You'll just have to take some time, think things through, train if needed, and breath.