Here is my view on this,
1) are marketing plan is only effective if you have a good Revenue plan; meaning if you do not know how you will be generating revenue how can you plan to market to the best audience?
I would prepare revenue objectives and target audience. then move toward goals and growth curb. once my measure are in place I would then try to find the best approach to get the best bang for the buck. If you find that your going after outdoor type of people, my guess is they are not online as much as the tech guy that plays half-life! Then once you have your action plan, make sure to track it! every day, hour, minute! see what works and what doesn't and modify. In the end, the more you invest the better the results but you will always have to be on top of it!
2) I do agree with the other comments, Natural (organic) growth is 20 times better than paid growth! Organic will stay and impact on the long run. I would try to get evangelistic followers that will promote your site and breath it on the daily. the more you get of these, the better the results. Make sure you get them involved and get there feedback. this will be more valuable than any PPC you can find.