About your niche keywords, check them.
If you used the free Google keyword tool, did you select the exact match? That's the most accurate amount traffic of the three. Your traffic will likely be somewhere between exact match and phrase match.
Second, you need to find the backlink strength of the top 10 results because those are the people you're trying to beat.
Either you pay for an expensive keyword tool to help you determine that competition, or you can use a free one because Google's keyword tool does not calculate SEO competition.
If you're a windows PC user, Traffic Travis is a good free tool to help you determine if a keyword is going to be easy to rank for or not. It's relatively easy to read.
Mac users, however, are out of luck. I would recommend you buy Keyword Elite 2.0 which works very well.
Or if you want to go the free route, then download the firefox plugin SEO Quake or SEO book. But then you'll have to count backlinks, check domain age, and do everything manually. It's time consuming.
The best option, when you're broke, is to look for the more common free ways of getting traffic to your website like guest blogging. Try to use methods that are not SEO related.
If you have a really good skill like computer graphics, php scripts, providing backlink, etc., and you have access to PayPal, you can oursource your services on Fiverr.com.
At Fiverr, you sell your services for $5 a time. If you're really good, you'll get a lot of people buying from you. Or if you need to outsource help, you can buy from someone on Fiverr.com.