keyword / marketsize question

So I've been looking up some keywords of topics that interest me and that I am quite knowledgeable in.....

The question I have is:

When someone is just starting out, is it better to go after a keyword with lower average searches per month (ie 2,900) and no advertiser competition, or a keyword that averages a large number of searches per month (ie 3,000,000) and large amounts of competition?

I think it is going to be extremely hard to get placed in the top ten on a search engine for a keyword that recieves 3,000,000 searches per month.... but this shows a large market size, therefore more people willing to spend money... perhaps an easier entry point??

On the other side of the coin however, something with only 2,900 searches per month should be relatively easy to place high on using simple seo and getting a few backlinks from articles..... but even still placing high will not bring in alot of visitors... and perhaps it shows a smaller market, therefore less people willing to spend money..... is this a harder or easier entry point?

I hope that this all makes sense....... I can explain further if there is any confusion.

thank you