SMS, Twitter, and email doesn't need to send out an ad, at least not for my Galaxy S3. I just click and then hit back button. As for FB, I just had it set to post with custom privacy, where only one person can see it. You can also delete the message after you post, while keeping the Hero Points.
As for you other question, when I first started, I also eyed Lumiere. After a month of playing and doing a colo, I realized that she isn't good for arena/colo. So I looked at Praline, which is slightly better suited for that type of event. But by the time, I got enough Hero Points, I was already sitting on tons of decent 5*, so Praline doesn't seem that enticing anymore. So I decided to save the points and use them on nontransferable pots or TE when I plan to rank in an event for a 6*.
If you put in a little bit of effort and, 5*s are pretty easy to get.