I'm a pure f2p, and Lucky board is one of the only events I spend coupons in. There's occasional other events that I might spend a little here and there, but Lucky Board is my main spending.

I just threw 4k coupons on it today! ;P

I got about 180+ Medium refines, and collected 1 Charms pack (just to check if it gives me spin, and it doesn't. Lol!), and collected 5 Sage Jiraiya fragments (to keep him at 100, so if I pull him, I can immediately 4* him).