Thank goodness I don't decorate my planner - I would collect and spend a fortune on all the colorful stickers and other embellishments. How do I know? Let me tell you about the 3 things that I do collect. I don't use them for decorations and I have plenty, but I still can't stop buying them!
1. Pens & Highlighters
It must be the color thing that propels me to keep added these to my collection. In my own defense, I might add that several of these pens and highlighters were "Secret Sister" gifts from some of my homeschool moms. In my planner I use a Sharpie pen (not marker) to do most of my writing - I occasionally use a red one to write in something I want to stand out. I use a highlighter to cross through items when they are completed. To justify the amount of pens and highlighters I use, I often switch out the colors I am using. <grin>
2. Clips, clips, and more clips!
Just like above, some of these were gifts as well, but I have purchased several of them myself! I use these clips to mark pages I want to get to quickly. For example, I have several pages of weeklies in my planner. I clip all used pages together to the weekly divider and am able to go right to today's date. I do the same thing with my monthly pages. I have used all the styles of these clips at one time or the other in my planner - love those oversized clips!
3. Sticky Notes
Ah, well - these things are more like an obsession. I also have these in several different shapes and I use them all over my planner. I have more of these than I will ever use but at least I have choices, right? Some of these have been gifted to me as well.