distributing user posted feeds to a large population

I making a mobile app similar to facebook as a college project. Problem I am facing is say if I have 25 users and 24 users posted something on the site of which user1 made the first post. Now say the 25th user logs in after two days. Initially I was showing the feeds in FIFO order. But if I keep using FIFO, 25th user wont be able to see the last post unless he has undergone all the previous posts first. Same situation in LIFO. If we scale up the app, the problem statement would be huge as there would be some feeds which will never be seen. So how do I tackle this?

I thought of distributing users into groups and show the feeds within the groups first, and then to the neighbouring group and so on.

PS: I am using meteorjs for building the app.