Hey! 
I've been marketing dating ads on FB for one year now. It's a great way to make some quick cash, but the problem/challenge is getting it stable....(of course).
I'd never had a dating campaign run more than 3 days.
Many people seems to do pretty good with PPV, even if the profit is 30-40 bucks a day it's still better if it's stable over weeks/months.
Which traffic soruce is most reliable/stable for you?
Regards,
Call3
my own sites that get 100% organic traffic are the most stable.
Too stable actually.
Adwords. Until you get a manual review...
direct to site media buys....no worries about loosing an account and less competition
^^^ definitely. Most avoid them out of laziness or impatience.
I cant speak on polars behalf, but depending on payout and performance of course it can vary. Ive had successful buys at $4-$5/cpm, but typically i look for the 50 cent to $1 range.
Media buying networks. Big hurdles. Account history. Little competition.
Out of everything i've ever done, SEO & Direct site media buys. These are also 2 of the hardest methods to scale big, so at the end of the day both these have made a lot less compared to other traffic sources i've worked with.
Also to add onto @combo's comment, a lot of direct site media buys are usually smaller sites (I've only bought traffic from smaller sites in the past). They don't work on CPMs, they go by monthly payments which are usually very FAIR payments compared to CPMs on larger sites. These are the sites where you may see some amazing ROIs, but these sites are also a pain in the ass to negotiate with. The best way to make it successful is to mass email as many as you can (only email 1 by 1), but email a lot of them because the response rate is low.
For me SEO and hand picked urls deep in a path on traffic vance
SEO & your own sites in a evergreen market.
One of mine has done a steady $300 a month since 2001 with an hour work a year to update some of the scripts 
AdWords, linking directly to eCommerce product pages with ShareaSale.com merchants.
Never have to worry about a manual review, but the store owners might not like that
I am sniping keywords under their noses. So far, no complaints or campaign hijacking.
Downside: it took a lot of effort to find a handful of products that net $250-300 per month.
Facebook for me. One campaign in particular.
Plenty of fish,
Gotta love the <50 log in XD
Looks like im going to have to take a look into direct site buys!