Let's say you have 10 related keywords. Each have around $250 in profit potential in terms of adsense if you rank #1 for the keyword in google. For these 10 related keywords you decide to make one site under one domain. For each keyword the page rank of the current competing sites on google are no more than 3, mostly 2's. Would it be enough to have one post per keyword, getting anchor text backlinks for each post? Or would you make multiple posts for each keyword and get backlinks for all these multiple posts? If you know the answer, your response would be greatly appreciated.
if they are all related keywords, then one post per KW is fine but you wil need the backlinks. page rank of your competitors is not important. check to see how many backlinks they have and from what kind of sites. i would however suggest you use 2-3 related keywords per post as building links using one specific anchor text will be risky. you should build majority of the backlinks uning your main KW but about 20-30% of the backlinks using related keywords per post to make it look natural
Building links is the answer. Use the keyword as hyperlinked to your blog post and get high PR dofollow backlinks to gradually increase your SERP ranking.