Singleplayer is a great way to learn, treat that car as if it costs you money when you crash it. Adaptive AI will give you strong and mostly fair races when you run against them a few times. Join the RaceDepartment racing club, they have regular races across all types of cars so there usually be something suited to you most weeks. Official raceroom championships probably aren't going to happen, not at this point in time anyway. There are lots of leagues you can join you race regularly against others though.