Not GP, but I stumbled across these [0] at a Barnes & Noble and have been quite happy. Take ink well (including from fountain pens), take abuse well (I regularly fold it nearly in half to have just a page on top). And it's very inexpensive compared to a lot of popular brands.

[0] https://www.amazon.com/Miquelrius-Leather-Cover-Graph-Notebo...

I use very cheap notebooks with a plain paper cover. I tried more expensive Moleskine notebooks a while ago and found a surprising problem with them. They were too beautiful to use. I couldn't bring myself to blemish them with my unfiltered flow-of-mind notes which would often turn out chaotic and stupid. I would only write things down selectively when I felt they were worthy and sufficiently structured. This would in turn inhibit most of my writing and significantly reduce the value of this habit. With a cheaper notebook the effect disappears. The less holy it is, the more useful it becomes.

On the other hand I highly recommend finding a really good pen to write with.