Hey Crachah,
I do advice you to be careful with Adwords. It works wonders if you know how to use it, but it'll suck your money if you don't.
For keyword services, I recommend two.
Google's own External Keyword tool. I guess you know about this already? You can find it when you are selecting the keywords to use when setting up your adwords campaign.
Another one I recommend is Keyword Discovery's keyword tool.
I personally prefer this over WordTracker's.
From what I know, Wordtrack based their results on 2 tiny search engines and multiple the results based on their search engine market usage to reflect the real numbers. Don't seem to be very accurate to me.
Keyword Discovery's is based on the actual search engine results. Not sure how they got the information, but I frequent to a highly respected
SEO forum and almost all the experts there prefer Keyword Discovery over Wordtracker.
Hope this helps!