Here are my additional suggestions form the post above:
1. Do survival, nine tails event to get coins and spend it on Eight gates, try to get purple ones and upgrade them mainly ninjutsu, taijutsu, life, def, etc.
2. Equipment Strengthening > although this will do a little increase in your BP but it will help
3. Try to explore the Cave for runes

Coupons no jutsu is powerful but Ingot no Jutsu is a high rank jutsu which will significantly increase your BP if youre a P2P player. :lol