Which machine to hit next?


I am new at htb and a noob regarding hacking. I am well reversed in Linux and networking and less in windows. I know some programming in bash, ruby and python.
I have gotten root on openadmin, which took me a couple of days to complete. There was a lot of frustrations on the way and I got help from the discussion about the machine.
But where to go next? I have my eyes on Obscurity, but don’t know if this is a good second machine for a beginner?

I hope this is the right place for this thread?