Disregarding the quality of user that come from adwords, I am still in the opinion of using adwords a media for advertising the forum is not the right choice. The best ads is of course from the content itself, create a content, link it to the other site or let google webcrawler do their job and let the site grow organically. It's not like there are a time limit or anything. Unless you are thinking to put the adwords here which I'm fine with it due to my use of adblocks.
Textfile Section, Original Write Ups, etc.. I also feel inclined to agree about organic growth, however, simple personal advertising across other forums can draw in a steady amount of new members more inclined to try their hand here since I would consider this forum relatively "fresh" in a sense. People like the idea of getting in on the ground floor and being one of the early members of the community.
As for the Adwords, I think $100 would be a sufficient and appropriate amount. I really don't think spending more would be wise or worthwhile. Again, this type of board has a certain niche to which is attracts new members.. while there are plenty of people like us out there, most arent actively seeking such a place because they are unaware of their existence or.. are doing drugs, busy crafting their hacks, or doing some other weird crazy interesting thing elsewhere.. The user-base will grow, just take more time. It's not something that really needs to be overly stressed or else you misconstrue the general focus of the forum and its members in the first place.