Your current team is alright for your level.
Another option would be something like

Sasuke - EarthMain - X
Naruto/Sakura - Hinata - X

This way you can get a combo with an accupuncture in it through using sasukes chase to cause repulse which hinata chases and causes accupuncture.
And putting earthmain in the first position to get his mystery off first.

Ninjas you should work on as soon as possible would be to get sasuke to 3 stars.
Start buying fragments from shops constantly, try to get kabuto, he is a really good healer and essential for certain PvE content. Also you could start farming fragments towards Tobi, he might get nerfed in the future so it's kind of a risky investment.
Otherwise it pretty much depends on what you get from scrolls / events / survival trial etc.
Saving up coupons for events is a good way to get more premium ninjas like Iruka, on the weird treasure events where you use keys and get deals from a treasure you can get him easily for like 800-900 coupons.