Optimal number of keywords, seo.

What would you say is the optimal number of keywords to target per site, let's say a micro-niche / niche Wordpress blog. 10, 50, 100, more? Why?

Completely impossible to answer at site-level, as long-tails and phrase-match/LSI keywords will make any numbers meaningless. Plus a site could have 10 pages or a million pages.

At the page level,it is generally best to target one specific keyword, using phrase-match and LSI variations as part of a diverse/naturalised anchor-set.

words that you want to promote +relative.

It's up to you and also depends on the kind of site you are using.

Generally, 1 to 15 is ok, so long as their is no keyword stuffing.

Does this go for a eCommerce site with like 50 products in same niche and that needs to be ranked for a bunch of long-tails and phrase-match/LSI keywords?

I am thinking specifically about a Wordpress (or other software) blog. I normally choose a niche / micro-niche, get a domain name with a keyword that has more than 1k searches USA on Exact match type in Adwords Keyword Tool (my decission also depends on SEO competition), and assign related keywords with quite a lot of search volume (usually around 1k-3k) as categories. Then I assing more keywords to these categories. So I get something like a keyword tree (I think Market Samurai uses this term). I target the main domain keyword, category keywords, and add longer phrase keywords also.

I guess it all depends, but I've been doing it for a while and I am wondering more about how to consturct a site based on all these keywords, and what is the best way to use them. I heard it is best to use one keyword per post, so I do that. I try to add one or two longer phrases to these posts also. I think there should be a genral answer to this question, but it probably takes a lot of time working on the websites to get a feel of how Google works, and know what works best, what doesnt etc.