Obviously, the answer to this question depends on your industry and what your keywords are, so we’ll focus on how you can find the answer instead.
The first thing you can do is use our own keyword research tool to discover how many searches are made for a particular term in a month. We also include variants of the keyword, similar terms, and the number of searches of these keywords. You can also check other keyword metrics using our on-site tools, which will point you towards any keyword opportunities you might be missing.
Another thing worth doing is using your Google Webmaster Tools account to check how much of your traffic comes from searches for your chosen keywords, which will give you a good idea of how well your SEO strategy is working out as well as how competitive your website is.