If you are new,do what i did.Go straight for power (things like charms material,cave keys,refines) and once you get close to,in power, as most people on your server (like top 50 at least),you can go for event ninjas such as minato,edo tensei deidara,shark fusion kisame,earth grudge kakuzu,edo tensei tobirama,hokage tsunade,swimsuit temari,angry kushina,angel konan and other expensive ninjas that we dont yet.Or,you could not go for event ninjas and * with treasure ninjas like madara,susano'o sasuke,danzo,darui,3rd raikage,hashirama,etc..You would be at a higher power than if you choose to go for ninjas.There's 1 person on my server who has high power (200k power) and a couple of event ninjas like shark kisame,edo hiruzen,both minato's,etc. but still rocks with the treasure ninjas like all day and does fine.Basically,going for power is the best option to spend your coupons on,and definitely focusing on initiative.