I think in terms of importance:

For Coins:
1. Group Skills (Effects Team)
2. Equipment Strengthening
3. 8 Chakra Gates

Than for your time:
1. Ninja Tools (Effects Team)
2. Battle Armor (Effects Team)
3. Summon Runes (Effects Team)
5. Equipment Upgrades
6. Magatamas
7. Equipment Refinement
8. Purifying Rune
9. Mysterious Cave
10. Tactics Page

Ninja Awakening and Fragments would be best left to the player to decide on their team comp.

Obviously my thinking is if you can't do one on the list, move to the next one.