Under a FIS the controller is obliged to tell you absolutely nothing about any other aircraft in you vicinity so using FIS as any sort of substitute for a lookout is a complete no no. Even under a RIS the final legal responsibility for collision avoidance rests with the aircraft commander. "No advisory avoiding action will be offered".
What I tend to do is once out in the practice area I monitor the radar frequency and from that you can get a pretty good idea of who and what is where although not every aircraft in the local area is going to be calling up for RIS or FIS. I will only call Radar/Approach when it is time to rejoin.