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Another thing to consider is the visitor/commercial intent of the specific keywords you're targeting. You can find that even very similar keywords/synonyms can have a different intent or level of customer awareness and even though they may be "talking about the same thing", you may want to create separate pages that match the searchers intent/objectives. Don't stop at the point you determine the keyword volumes and whether the keyword is relevant to your business/services/products, but ask yourself "what is the visitor looking for/trying to do when they search for {query}" And take a good look at the search results returned from each keyword it can tell you a lot about how both google and your completion view the term.