When you first off start on a server, spend 500-800 coupons on magatamas to get a solid competitive edge.
After that ALL you do. I reiterate. ALL YOU DO. is just save for lucky board for a whole month. Then you use it all on lucky board. And you only buy power options. F*ck fancy ninjas. You will beat people with Konohamaru Corps if you have enough power.
1. server starts, spend on magas and maybe refines to get a competitive edge
2. Only spend on lucky board.
3. Only spend on power.
(4.) Once you start hovering around 30-40k mark and your BA and refines are looking good, you might want to consider finding a good deal on Treasure of the Sage for Cave Keys, Mood Scrolls (these you will get passively so not to worry), and even summoning scrolls (surprisingly large amount of power here)
On redemption merchant, same as lucky board, F*ck ninjas. Buy coins with arena points, Low refines with Ranked points (until you dont need them), and Med refines with Group points. And Runes with Summon points.
Power is the main thing to spend on.