I have a friend who did 120k on tree, 40k till he went to lvl 7 then 80k spent and he got 80 frags of Asura and 36 frags of Shisui. he was aiming for Asura.
I was thinking that it doesn't worth but at the end it seems it's the best event to get Asura at the moment.

Wish you the best.

if one plans to do tree you must decide early in the first 2 days of the event, because you will be able to fully redeem the power options as there are daily limits. For me asura turned out to be 1 frag per 1500 coupon spent but still it was the best choice for me as a f2p to get his frags. I got equal amounts asura and black zetsu and with the fuku pack enough to 4 star asura. Shisui definitely is lower drop rate. If you decide too late, there are next 2 weeks to see if those events are good to spend for this 110k fuku.

So i spent 136990 coupons on the tree

37400 to get to lvl 7 (according to Ice*, didn't count myself), so 99590 spent at lvl 7

What i got:

96 Asura frags (i had 4 already) : 1037 coupon per frag

36 Shisui frags : 2766 coupons per frag

102 Zetsu frags: 976 coupons per frag

Also 4 Kinkaku & Ginkaku, 8 Neji, 3 Deidara frags and some other

Had 30k coins after all this. Bought Obito, not sure if i should buy another 100 for 4* (4k coins), Pages packs (4k), Potions packs (3k), have 20k left now