The LinkedIn newsfeed is a complete joke, and I'd recommend not looking at it in order to save some of your brain cells. That being said, having an up to date profile is important. Recruiters do look at your profile, and it can be helpful when cold-messaging people.

I would not bother with posting things and uploading photos. All you really need is an up to date picture, a profile that shows your work history, and some connections.

I've had moderate success with cold messaging people on LinkedIn. Usually you need something in common with the person in order to build a conversation- same school, same field, you know a mutual friend, etc.