Yup, the luck wheels are double edge swords for f2p since you can either get lucky and get really good ninja or end up with waste coupons for for at shop price items. The lucky board is one of the better f2p event do to most of the rewards on the wheel being better than shop prices, the going around prize being generally pretty good if your going deeper in the board, and the board generally having clothes at decent prices allowing you to pick up potent bp for about 5000 coupons which as low spender you can get in roughly a month and a half and as a f2p in about 3 mouths early on. Myoboku is also good for f2p since one spin of the wheel is not bad price wise and doing the trail is easy and can net you 420 coupons over the cycle. Great plate is excellent since the full week versions and 100 coupons can net you the first prize, though great plates is more limited in variety being frags of characters (great for free but not super recommended spending on) and a few power items, as an example getting about 70 free myoboku scrolls from last week on free accounts. Don't expect to get the ninja prize frags since its 35000 coupons for right away recruit.