First art journal - backgrounds

Ok, I've never made an art journal before. They always look so cool, and I really like the one in this class. So I'm going for it! I'm going to try some things out and see what happens! I have some thick cardstock that have kind of a coated feel on one side (they're actually comic book backer boards) and I cut two in half. I don't own white gesso, but for some reason I own a jar of black gesso which sits with my craft supplies and taunts me because I have no idea what to do with it. So two pages got black gesso, one of which I scraped some lines into. I also own four gelatos that also sit in my craft supplies and taunt me, so I used those on the coated side of the papers and thought they smooshed around well with my fingers, and then I sprayed them with water and they spread around much better. I also tried them on the black gesso, and wow did they really smoosh around with my fingers. They kind of show up on the black gesso but obviously not that great. So I really want to go buy some white gesso! I wasn't too worried about it because I'm sure they'll be covered with paper soon when I start the next lesson.