If you aren’t at 1000 views, not much as far as advertising is going to work for you. All depends on what type of forum you’re running, how you want to show the forum off, etc. If you’re running a forum purely for the intent of making money, you’re going to have a bad time at the start. You won’t be making much even once you have quite the active forum - maybe enough to cover cost.
The best plan is to not consider monetization at the start, and to only figure that out later, once you have a loyal userbase. Nothing alienates potential new users than a slow community and an ad on every pixel of the screen. You also have to consider what type of forum you are running / what content will be hosted as that effects what adverts are shown and how much you get per click per view.
As for how I would do it on a general forum with no specific niche, probably have promoted posts and/or advertising above content as the sponsored by section. There is no default advertising plugin or backend solution for advertising as far as I know in discourse so this would have to be done by hand though I imagine not too difficult. The only forums I can think of that have advertising built into the system is IPB and vB, though I’m not too familiar with vB5.