Niche discussion forum promoting

I recently received a discussion forum from a friend, its a specific niche forum (a scale models forum) Looking to start and promoting the website. I only have few registered users and need to add more users (legits only, not fake/ spam/ etc) which ofcurse make more posts, and elp this forum grow. any other suggestiond would be highly appreciated. Im on real tight budget so basically- name your price! Im looking to add 40-50 users to my forum. URL will be sent upon request. You may use facebook advertising, google advertising or any method you want to bring users. Again, legit subscribers ONLY. Its easy to identify fake users on such niche sites.