I started sketching on cheap plain white pages sketchbooks. At that time my sketchbooks were a mix of planners and sketchbooks , I put everything on it, stamps, addresses, phone numbers , sculpture projects, collages, reminders, you name it , I sketched with the same pen or pencil I wrote. But one day I bought a watercolor case at Venice/Italy and then visiting Toscanny , I tried to use watercolor on my sketch of the leaning tower of Piza and it was a disaster, I had to start the sketch again because the paper waved so much and was so soggy that I had to eliminate the page. 
Cheap plain sketchbook, black fineliner pen and color pencil

Bic pen o n A5 cheap sketchbook
Back to Venice I bought a wire bound , 170gsm, Canson sketchbook but still I didn’t like the paper too absorbent , and too thin, it waves with the watercolors, and that wire and all those holes made the pages very easily detachables. Anyway I fulfilled it until the last page. After that I bought all available watercolor sketchbooks brands ( as you can see on my previous article on my blog) after all I need my gear work with me , not against me. That’s why all the fuzz about sketchbooks.

HB graphite pencil on a A5 cheap sketchbook (all sketches from 1994 and 1997)
By the way I’m waiting for a stillman &birn wet media, square sketchbook , these days at the mail, and I ‘m so excited about it 😜👋