I have discovered that with many things, simplicity is everything. The simpler your header is, the better, and the more fancy and professional it looks. By simple, I don't mean it will be easy and plain, necessarily. My current header took hours, but it isn't too bright or overdone like my last one.
Neutrals, black and white, or pastels tend to be good colors for headers. To avoid over-dong your header, try these tips:
1. Only use text (and up to one picture or additional design, if you really want to).
2. Don't use ugly fonts. I though my previous header's font was cute, but now I think it looked dreadful. I suggest you look for minimalist or calligraphy fonts.
You can find cute web design templates on Etsy or Pinterest, if you need some inspiration. I hope this benefits beginner bloggers!