Cave keys, refines, ninja tools, threads, charms, costumes, mangatamas, purifications, ti tools, ninjas at home, summon cultimavtion, summon runes, myoboku, etc . Whether you are at 10, 40 or 150k power pretty much only thing that changes is basic -> medium -> advanced in front of refine/thread. You gain power the same way as you did before, the same way as everybody does at any level. Just do your stuff, hoard items, spend them during rebates.

As a fellow f2p, allow me to give you one of the best avice I got.

Stack position 1.

You power up all members at the same time only if you are p2w.

BP is mainly from refinement and cloth and rune stones.

Do Purification ONLY after your equipments have been refined to a high enough lvl, say lvl 8.

Charms also play a major part.

ps. I know you didnt ask this but in terms of ninja, Han really helps since alot p2ws are running flower guard with wind main and root with lm, and obviously em has shields.
:)

dont level up and stack up for great plates

Level freezing is only good for P2W players since they dont have to worry about the higher lvl stuff since they pay and they get power

THIS is the answer i wanted to see , thanks a lot man #F2P

Not exactly true. It has benefits for every players.

Check your "Power Up" *ttttttttttton once in a while and see what you're missing.

Most of it is full , except upgrading stars :) dont worry , i am checking it in a while