Mostly have a PR 3-4 , and I don't really care about alexa rating (and it seems some of paid review broker don't care either).
Blogsvertise, smorty, and payperpost mostly will accept it But Payperpost as I said is looking for quality blogs, if yours accepted by PPP there are many opportunities even for PR0 blog and if your address is in US there are even more opportunities (some advertisers want blogs with US address because they shoot US market). Also with PPP on Tuesday sometimes available $50 opportunities (they call it Tuesday 1K -- if I'm not mistaken) and blogs with PR 0 also eligible to grab the opps.
The best appraoch would be a) Submit your site to sponsored Reviews, payperpost (to earn in short time if you can write smart stuff as chances of rejection are high at every level) b) Add nice adsense scripts c) Make sure once someone reaches your blog, should be hard for him to leave (if not your content, you ads should be smart enough for e.g. banners etc.) d) Increase monetization with doclix for adsense e) Use more PPC advertisements f) Maintain neatness on your blog, clumsy blog cause more bounces Last but not the least, write unique and good content..sooner or later you would start earning. Once you get good PR update, automatically you would get traffic. With my experience, if you try to much hard to monetize nothing would come.. so be a nice blogger write good weblogs 3-5 times a week and forget about your blog for 4-5 months. Do keep an eye on your stats and this can be achieved only when you have your own blog - not hosted with blogger. You would not be able to own it once it starts laying golden eggs.
My advice: don't use any of these on any site you care about. Google aggressively penalizes anyone that gets paid to post. If you want to become a blogger who makes money for writing original content and learn to generate a monthly income based on that - get your own web site, post your own content, and learn as you go. You could even learn from my mistakes!