I think results depend on how you use groups & pages on Facebook. Like many here have said, if you join an existing group meant for Internet Marketing, sharing, business promotion, etc., your posts will just get buried in spam, and your audience in those groups is other people like you....people looking to sell, not to buy.
One alternative option would be to create your own group page. That way, you are the administrator and make the rules. I think you can even sticky posts, add a link in the about section, and other things to make your content the most important in the group. This isn't a quick fix, though, because it will take time to get group members through FB ads for likes and other sources, but they will be more targeted. If you make the group about more than just you links (add value, like you would on a blog...maybe even tie it to your blog, if you have one and they are the same purpose/niche).
Another option may be to narrow your niche more, in terms of the groups you look for. Think about what you are selling and where people interested in that may congregate. This is a bad example, but hopefully gets the point across: maybe the "make money online" group is spammy and useless, but if you are selling an email marketing system, maybe the "email marketing products and reviews" group gets more quality traffic and view time.