Early you must not worry for ranking,just get lvl 60 and stop doing main quests,lvl up only from daily exp.It will be something like 3-5 days to lvl up that way.Save coupons and spend only,repeat ONLY on lucky board.Get as high as possible on ninja exam,it will help you great for magatamas.Dont skip nine tails invasion,even if not perform well there.Save seal scrolls,summon scrolls,cave keys,charms,refine runes,only use them on rebate.Always do matsuri,sage battlefield.Get Hinata and Kabuto as fast possible to 5 stars,that way you can get Iruka for free.Dont skip Great Ninja War,and group summon

Hinata and Kabuto for 2 reasons-they are usefull,and its easy to get them 5 stars.As falling back in terms of power,rebates are every month,so little power you miss not using refines,charms,keys right away,will pay off when rebate comes.Recomend to stop doing main quest at lvl 60,or even before 60,so you will lvl at slow pace,getting time to build power,as at same time not fall way back behind other players in term of lvl.I stop at 65 lvl,now im 84 lvl with 55k power,when most of players at my server are 87 lvl,and 45k power .

I save stamina for events,there is one that give points when sweep instances,i use potions for that.Other good use is when sweeps drop double items,dont remember which day was it

Only avakening materials and equipment upgrades are double,ninja fragments not.Sasuke is realy good at 3 stars,and later on you c*e skill books(buy with fragments),when he is 4 stars.Always focus on power,there is some ninjas that help greatly to progress tho,but you must have patience and some luck to get them(Naruto sage mode and Mei Terumi,they are realy help in high lvl ninja exams).For priority i say focus on equipment refine,battle armor and summon cultivation,they give good amount of initiative,second is equipment streghtening,upgrade,group skills,summon runes.