I think the best available option is to start posting new content on these sites. You can buy tons of traffic but it will not help you to improve your rankings and only hard work on these neglected sites will get you some organic traffic in a long term.
So, try to post a one or more (preferably) posts on these sites every single day and I am sure that after a one month you will see a massive improvement with the SEO.
Do not hire a cheap SEO guy because he will most likely do more harm than good. Of course, that is just my personal opinion.