There's not really a "magic number", even though we have seen things start to snowball for pages when they are closer to 1,000-2,000 likes. However, if you're a small business in a small town you might not ever get up past 300 likes and it might just be more about engaging those 300 instead of going for a large number of likes.
If you're company has a large audience, national or global, you might want to try buying some ads to establish an initial base. You could also look into some PR to help spread the word of your company.
Social media takes patience and time, keep posting consistently and test different posts to see which gets a better response. You might want to focus more on the 139 fans you currently have and encouraging them to ask their friends to like your page versus always targeting new fans.
Hope this helped! Thanks for reading!