Well, I have done a little more research, and I decided that maybe I don't need a filter. Without a filter, it will still cycle, right?
Maybe it was a mistake to completely break down the tank last week... but I was just fed up with the overgrowth of algae and all of the grime I saw at the bottom of the tank, even though it was mostly just bits of algae that I had scraped from the side of the tank (it STILL amazes me how little poo bettas make) and I just decided that I wanted a sparkling clean tank...
Anyway, I still want some answers about gravel. There is so much conflicting information online. Some sites say that you can't have marbles because, since they are round, they create a bigger space in between marbles for gunk to collect in, and some sites say that gravel collets too much bacteria, and helps make the water dirty. I know that some nice, bright blue or black gravel would really make the colors in Mr. George stand out. But I'm afraid maintenance will get harder, and it might even reduce his health.
Please, I guess all these replies from me will make people think that my questions are answered, but I still want help! Sometimes it seems so unfair that some forum members only look at threads that were made by members they are friends with, or they leave some threads alone because someone else answered them... I usually don't answer on threads because I know I'd end up giving out the wrong information--that tends to happen to me a lot--and I just really want some simple opinions.