I have a gambling site which has not bad performances in Search engines. There is a problem with the subsection about casinos, the main keyword is "free online casino games for real money" and the link to the subsection is here: http://www.slotozilla.com/free-slots/real-money .
I'm not using geotargeting or anything like that. I bought some natural links and some blogposts, but I can not detect why does it loose positions from time to time 1 to 10 positions for each query per week. Can not detect what is the problem?
Maybe the problem is in the relevance of the article to "online casino games" ? There is no incomings in text

Is here anybody who can detect the errors in my strategy? Will be greatly indebted, if you have any questions - you are welcome.

There is no error in strategy as soon as google relize the site about porn and gambling google back thier site in every update or every week so most of the gambling site owner rank one time after that they will penlize by google and then they make a new site.

But the other pages and subsections are going well, so that's a problem, I can not understand how to lead them to the TOP. I worked previously with gambling websites, but now I can't believe that the query "free online casino games + for real money" are so hard to lead in top. Maybe, in articles near the URL there is a commercial incoming of "for real money" and should exclude it or write farther from the URL?
How ddo you think, is it important or not?

I remember that the queries like "buy the product + low price" are not using in anchor texts, for example. Maybe it is the trouble?

I bought some natural links and...

Bought links are not 'natural'. Make sure they're tagged as 'nofollow' if you don't want to risk getting penalized by search engines.

the site seems fairly well optimized, keep evolving it and it'll likely build more trust with the search engine over time. Steer clear from artificial link schemes, develop a more powerful internal linking structure instead. You're on the right track though. Make sure your textual content is original.

I think on page optimizations technic check woorank through and then modife your website.