Cotton probably isn't the best to start out with, it doesn't have as much stretch as other fibers which you need a bit more than in crochet. And since the bamboo needles are 'sticky' and so is the cotton, that makes it worse. I'd say go for larger metal needles to learn on especially if using the cotton, but keep the bamboo 8s too, because a thinner yarn or one that's more slippery will be better with them. Or if you have some acrylic use that with the 8s.
sue- knitting heretic