KW/site structure

I am running some blogs with a single keyword assigned to each page == for instance 200 different keywords of a superset like "forex". Results are ok, but not fantastic. Does it help for ranking to use only a small amount of keywords - e.g. 10 - and having say 20 pages per keyword?

How do you build your sites: one site and one or some keywords or many pages where each has its own keyword assigned?

cooooookies