Hi! I personally think what you said was definitely a great way to use your resources. Collect the resources you need and wait for a rebate event.

Tactics is something that does definitely help in power and my opinion is to power it up to probably around Level 6 (remember to choose the one you want to use in the long term, I personally like Ghost Tactics just for general purposes).

If by chance you are wanting to focus on Battle Power, I personally would recommend focusing on Beset Magatamas, Charms, Rune Stones, Myoboku Trial Cultivation, Summon Cultivation, Treasure Tools (from Team Instance), and Treasure Tool Essence. Obviously there are many other ways to obtain power, but those I mentioned are my opinion one of the best places to get power. Just do what you are doing, collect power items from events like Treasure of the Sage, Konoha Shop, Lucky Board, etc. Save them for rebate events and use it.

Hopefully this helps!

~Jib