With the current amount of series right now I just buy Rokujouma every month and occasionally buy books from Grimgar, Arifureta, and Realist Hero which I finally caught up to the latest release of both Arifureta and Realist Hero. Next time I buy in bulk it would only be Rokujouma and Grimgar unless there's an update for the other 2. I'm also thinking on buying Paladin but I'll have to wait until JNC starts updating again on January.
Even if the only bonus contents are just textless illustrations it's still okay with me because they're DRM-Free. I just don't like using the e-Readers that are required by DRMed e-Books and also the format of how the text and images looked like in the e-Book itself so I prefer just extracting the text and images and creating one myself and using my own preferred reader to read them. It's something I bought with my own money so I should have the freedom to use it however I want rather than being restricted to read them only on certain apps with their not so good format.