What was your last anime related purchase?
Kagerou Daze (light novel) vol. 1.
What do you plan on getting next?
Still no idea but under the assumption I go back to the store I got the light novel from, I'd go Orenchi no Furo Jijou vol. 1 (manga) if not the answer below.
What do you regret not getting?
One Punch Man vol. 1 (again, manga), it was sold out when I got to the store...(I checked it out online the day before and it was in, but the online version of the store doesn't say when stock is running out.)