I would not suggest using Bing at this time. Their advertising system is hard to manage, it's more complicated than GG Adwords. And it's not flexibility to add some features such as negative keywords....
So with a limited budget, I suggest you focus only on 2 main platforms: Facebook Ads and GG Adwords. With Facebook, you can create your own Fanpage first in order to run Ads, try to focus closely to your campaign and your products, targeted audience only (use Post engagement and Fan like). Using GG Adwords to drive traffic to your website by potential keywords that user are searching most.
The reason that I suggest using 2 platform are that they have the features to target detail on country, gender, platform, interest,...and many thing others.
Hope this helps.
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