it doesn't matter whether they are posts or pages as long as they are meaningful (they contain unique content that helps your visitors). Google doesn't discriminate between pages and posts when it comes to SEO so don't worry about that.
Regarding the content strategy.... just make 10-20 posts (content posts I mean, not pages like Contact Us, About Us, Privacy Policy, etc.) initially and then post at least 1 post per week for 1 year. You can post more if you want, but I wouldn't post more than 1-5 times per week if your domain is new. The thing with Google is that it wants to see freshness, relevance and consistency. These are your main weapons as a beginner so you will want to post as much content as humanly possible, to make it as relevant to your keyword / topic as possible, and to post content consistently. Even one single article per week (or even every 2 weeks) but which gets posted every single week for all eternity is better than 100 articles posted today and then nothing for 6 months. So, consistency, consistency, consistency.
And it's better to target low competition keywords first instead of high competition (high traffic-ed) keywords because your site is new and you need traction in order to improve and consolidate your rankings. And as your site starts getting organic traffic (which will probably happen after at least 3-4 months, maybe more, if you are being consistent with your posting) and starts ranking for all sorts of weird and unheard of keywords that you will not even know exist you will also start ranking for higher competition keywords, and at that point you can start targeting high competition keywords if you want to. But in the beginning it's best to start small.
Also, you didn't mention this in your comment, but I am saying it anyway because it's important. So, backlinks... some sites do rank based on content alone, but most of them won't rank anywhere, no matter how good the content is. So, you need backlinks, and you need quality backlinks, too. Crappy backlinks don't do the trick anymore, and if you buy those backlinks when your domain is new (and clean) you will shoot yourself in the foot and delay its ranking. Better to acquire 3-10 backlinks per month but - again - do it consistently for 1 year instead of getting 1000s of backlinks from "SEO packages" that promise you 100 web 2.0 backlinks, millions of social signals, edu. profiles and all that crap. If you do this - I have done it on one of my sites last year - you are just shooting yourself in the foot like I said. So, get quality backlinks and even if it's fewer of them as long as they are quality backlinks (from guest posts on sites that are RELEVANT to your niche, have decent DA metrics and which also get organic traffic from google) it will MUCH better than getting 1000s of web 2.0 and profile backlinks on spammed (easy and free to get backlinks from) sites. But these backlinks will probably cost you dearly, so be warned!
