Best way to test various keyword phrases for possible targetting?

I would like to test various keyword phrases to see how highly they get in Google ranking compared to other keyword phrases I want to test.

So I am not looking to see how high they can get compared to other sites. Only against other of my own sites I may quickly build around other keyword phrases.

So for example if one of my test "sites" makes it to position 100 and another ends up way down at position 300 I will focus on creating a real site around the first site.

That way I don't have to throw any money down the drain for registering duds as has happened to me before.

I would focus on those keyword phrases that get higher up in Google than others and build regular sites around these.

So what is the best way to build pseudo sites to test keyword phrases?

Here are the options:

- subdomain off my regular computer consulting business site (which would have nothing to do with the subdomain topics I might want to test). For example...this-is-my-keyword.somebusiness.com
- wordpress blogs set up at wordpress.org. Keyword rich up front as in this-is-my-keyword.wordpress.org
- a free site built on some of the free web site places.
- Google's blogger platform.

Which of the above do you all recommend and why?

I am leaning toward a subdomain off my business site as I will have complete control over meta tags and otherwise for better initial SEO positioning.

I suppose I could try a limited Adwords campaign for each phrase I might want to test but...well...that takes time and money and right now I have no money to spare as I need to get another computer (this one is on it's last leg).

The other problem I can see is that once I decide on a few keyword phrases to target and take these temporary locations down, Google will still have them indexed such that the temporary stuff might compete for a while with the new sites I build.

Thoughts on any of the above anyone?

Thanks.

Carlos