These things go up and down. I am personally very skeptical that one can do much (or even should) to increase traffic other than write original, quality content. We should not delude ourselves that we can actually make a living doing this, certainly not in the early going.
I've been here only five months (a relatively short time) and I have yet to make my first payout with Adsense Google. It takes a lot of time. I'm thinking of applying for an Amazon account. But I am conflicted. On the one hand I do not want to make my hubs shamelessly commercial, especially since I don't write about commercial topics (I don't write for the clicks). On the other hand it might do well to break up the extra white space. You know what I mean?
The reason most of us bother to include pictures and videos, is because few people (especially on the Internet) can stand to read reams of prose on and on, especially if the articles are very long, without anything breaking them up. I am considering getting an Amazon account in terms of hub design reasons; but I don't want to scare off potential readers by seeming over the top with promotion.
Fellow hubbers recommend many stategies. Over time, perhaps, one can get some good income from HubPages (money should not be the prime motivation) -- rumor has it there are some people who make hundreds even thousand a month -- perhaps.
I would refer to a hub written by a hubber called Aya Katz called "Should I Backlink My Hubs," or something like that. I would recommend you read that hub, think about it, and then decide how much time you want to spend (or whether you want to) "promoting" your hubs.