This is generalized list I give to new players that ask in my server:

1) Save Refines, Threads, Charms and Cave Keys for the Rebates that use them.

2) Spend Moon Scrolls on Myoboku items until all 3 are at level 9, then spend on Cave Keys

3) Spend all Sun Scrolls on Advanced Refine Runes unless you need Assist link items to activate a Bond Skill

4) Save as many Coupons as possible for Fuku Deals, at the very least 10,000 Coupons but preferably a full Fuku (20k+)

5) Buy Command Flags/Training Potions with Coupons during Fuku Deals

6) Unlock a Ninja Assist Card with a Command Flag and then use Training Potions to level it to 5.1 (First spot on level 5, has Initiative) then repeat this

As for leveling up, there is little point freezing ones level (avoiding any EXP gaining events/functions) if you are not on a brand new server/cluster. You will be losing out on resources for almost zero long term benefit.

Hope some of this helps!

Magatama will build up over time from Ninja Exam, 9 Tails Attack and a small amount from Events.

Advanced Refines primarily come from Groceries Shop, Space Time Shop and Sage World Battlefields.

All of the Threads except Advanced come from Strong Approaching, with the Advanced Thread being primarily from events.

Training Potions come from Groceries Shop and Events. Command Flags (or the fragments of) come from Events.

Rune Stones come only from Cave Exploration. Edit: Charms come from Events.

You can get pieces from the Events each week without spending any Coupons/Ingots, but it will take a long time (especially once you start getting high in power).

Typically its best for F2P or Low Spending players to get 1 Carry Ninja (Like Edo Minato, Kushina Red Hot etc) and 1 Support Ninja (Like Edo Itachi, Ibiki, Kurenai Summer etc) and then focus most Coupons on gaining Power Items from events during Fuku cycles (Maximum benefit).