At an interesting crossroads... now what next- should I focus on facebook, Pinterest or SEO?

Hey everyone,

So the site I built a few weeks ago is now looking good, and I've got 7,500 followers on pinterest now, a connected Facebook page and starting to rise in the SEO rankings, getting a few clicks too though not yet sales. I now have to make a decision and decide which avenue will lead to making most money longterm for my site as of course I will be too thinkly spread if I try to do all three at once.

The SEO KWs I'm beginning to rank for are long tale, and have between 50- 300 searches a month, I'm starting to reach the top 20 for a few of them so a bit of more work needs to be done. I've been creating backlinks by uploading some of the infographics I created for Pinterest and putting them onto Document sharing sites.

My pinterest Pins get a modest number of repins, but nothing huge to shout about yet- but I've learnt how to create simple and quite good images, it's a matter of testing what works best and starting to get the hang of it now. I am also direct linking to affiliate offers away from my site on here so am testing quite a few things some of the affiliate offers are getting a small number of shares.

Thirdly I've been looking at facebook Ads to boost my page, I have used Facebook ads before- but because my page/site focuses not on a single niche- though several of the niches tie together- I may need to focus it more (or maybe create a page for each seperate subniche)

The way I see it is that

1) Facebook ads will provide the quickest results- I will know if a post leads to positive ROI quickly or not, but I'll need to do more work on the page/brand, or split the page into two or three seperate pages.

2) Pinterest- I could learn it much more and really figure out types of images that go viral, or the trending items etc.

3) SEO- the hardest work and most long term but may provide the best results long term overall.

How would you proceed, what would you focus on?