Yes, I agree that 12 neons might be too many. I had 3 neons in my smaller 29 gallon tank. It was nice to see them school together, so I kept buying more and more. Then I noticed that when I got about 7 or 8, it rather looked crowded, and although they were still somewhat schooling, it didn't look as nice because there were so many of them in a rather smaller space!
I like the suggestion made by dangerdoll for ottos. They're relentless workers and are really interesting to watch. In my opinion, 3 of my ottos have done a better job keeping algaes off than any single pleco or other types of algae eater fish i've tried.
Plants add much more challenges to your tank, but if you get a hang of it, it'll make the tank look a lot nicer and much more natural. I would say get a hang of it with some hardy fish first and then look into plants that are easy to keep and doesn't require strong lighting. Personally, Anubias have always been my favorite for smaller tanks because they're very easy to keep. From my experience, they don't grow as fast as many other plants do, but that can be a good thing too since it won't produce much shedding leaves