Always You can give wrong tips on forum, there is chance that Your opponents read them and use them, and in this way it should be easier to beat them in future...
Do I get anything out of that?
You also get a free month supporter if you help the old lady cross the street, but you have to send a photo for evidence to one of BBs.
The biggest gain from the forums is to read what others are writing and learning from that. Then after a while when you have learned a lot about this game you can fell good about helping managers that ones was just like you.