Just realized this wasn't here yet so thought I'd post it.
This shows the number of perfume you need to use a shelled item. Pretty self explainatory really

For the ones that say you need 0 perfume you still need 1 perfume to open the window to change exclusiveness, but the perfume won't be used.
Edit: Since someone asked, the Rarity and Level in the chart refers to the equipment, not the shell.
Please note I'm NOT taking credit for this. I didn't make it. No idea who did. Since the original is on imageshack (and the person didn't put their name on it) it's pretty hard to find out who made it. If anyone knows, please PM me so I can give credit to them. Thanks.