Facebook group infiltration (ninja mode)

I didnt fully understand your situation, I mean, you say that you are sharing content directly to the groups members, instead of posting in the groups to avoid any troubles with the admins? Is that right?

If thats the case, well, I think its quite a complicated job, you need to write each and everyone of the users and that can be a difficult thing, not to mention Facebook can banned you for doing that at any time.

I had a project a few months ago were I had to work with facebook groups, I had to build a group by stealing members to other groups of the same niche, I worked during two months on that assignment and I could only get to 500 members, adding 10 members every day, it was a nightmare.

After ending the project, I realize that my main mistake was to focus so much on adding new members, and not creating a single piece of content to build a community in the new group, if I had done that, new members would probably start to add them selfs to the group.

So my advice would be that you should try to create a new community, instead of just using the ones that already exists.

Anyway, you have also mentioned that you spent 100 dollars on FB ads and you didnt get any result, I think you should check what were your mistakes, maybe you could share the campaign and the segmentation you have been using here so we can help you on that.