Mostly you will get 2 stars from each spin and that cost 20 coupon. While med refine only cost 15 cp/each, as a f2p I do not find this event healthy for us.
Also GNW Tenten is not that good atm, she will comeback again in Mabui's shop fuction or another events anyway so no need to rush.
Gakido and Ningendo are good but meh, too costly to get them and they fall off later as we process to newer patch.

Oh right med refine cost 25 not 15. My bad, yea if you go for med refine it's worth I think.