27k coupons will get you to near the end of page 11 (due to each page returning roughly 1.5 steps worth of scrolls during one of the steps). The power gained depends on your ninja's mood and star count, as the primary stat bonuses from myoboku is amplified by mood and star counts. With 65% moods, 4* ninjas, you will get about 8500 power from it. You will get +480 init per slot.

PS: 27k coupons are not enough to go from lvl 7 to 10 refine safely. If you start at level 7, (instead of 6 or 8), you want at least 1200 adv refines to be safe. I've experienced far too many lvl 7 rank ups at 19x/200 and lvl 8 rank ups at 49x/500.