Note you could earn all currencies from all modes while Currencies will collect based on how you perform.
This means you could play and make everything in single-player, or play and earn everything in Sport Mode from friends. You can also earn a whole lot of Currencies before you have your first race potentially earning many rewards. Gone are the permit systems, and there are no seasons or tours; you can make all your credits but rally race GTSport time trials assuming you are willing to put in the time.
Of course the game encourages you to try out all of its systems, particularly with the Achievements you can earn (which are different from PlayStation Network Trophies). But unless expertise completely every nook and cranny of the software and you would like to collect everything, you are never required to do anything.
Further, even the Trophies themselves encourage quantity over quality. Most are about the number of the length you push and races you participate in, not any mode you may or may not explore while gold times in the Campaign revolve around.
Nothing in the game demands that you have a PlayStation VR. While there is a VR Tour manner, there are Trophies or no Achievements that need the hardware.
Gran Turismo Sport features a simple but robust internal sharing website for players to swap and like photos each other's liveries, and more. Sharing your photos outside GT Sport's internal sharing site is a little more involved. You will need to take advantage of the firmware of the PlayStation 4 to share a picture to flow races on Twitch or YouTube, or on Facebook or Twitter. This is a design decision but either way there isn't any simple means to share anything. Luckily, doing so is a Chat button press away.
 
         
        