Hands down the supply I have and use the most is paper! I am running out of room in my scrap room to keep it all - it is stacked everywhere! I need to work faster at using it up - not buying more would probably help out with that!
Definitely paper. I use my Silhouette to create 99% of my embellishments...so I don't need stickers and such. I also have an embarrassing amount of Project Life cards...