Please don't give SAM advice.
Stacking Regain/Store TP atma is terrible advice. If you want to increase WS frequency, Apoc and A&O will contribute more to that goal than Sun Eater.
If you can't comfortably 5-hit with your weapon and gear selection, try a 6-hit with Sword Strap. If that doesn't work, try a 6-hit with Rose Strap. If you've got very good gear and a 480-delay GKT such as Kikugosaku, a 4-hit build is possible.
Depending on what you're fighting, you'll typically want some combination of Apoc, A&O, Razed Ruins, and Voracious Violet. Only stack regain atma if you're not engaging and are there for red/blue triggers.