That's when you just save the runes and buy during a time when you do like the items. xD
It's not like the runes go away every month.
Lately I've been just buying one of each, using the runes I get as a member of staff.
I just really liked the rainbowy item this month, so I bought three of those. I liked the darker item as well, but I don't think I'd ever need to wear two of those poses at once so I only got one. And I've yet to gain enough to get the Aurum item for this month, since I haven't been posting lately.