Raceroom
If you find you don't get on with rF2 I would actually recommend you buy the raceroom premium pack:
http://game.raceroom.com/store/pack/premium-pack
It contains all the content in the game and is by far the cheapest way to get everything. All of it is top notch and requires no tweaking (other than your global FFB settings) to get it up and running. There's easily hundreds of hours of content there and you have the ability to run championship seasons against the AI as you please.
If you do go ahead and get it buy it using VRP which you can get for a discount here:
https://www.raceroomstore.com/shop_en/list_page?cat=24
Then buy the pack I linked above, it works out cheaper that way.
Do not, under any circumstances, buy content for Raceroom via steam, it's the worst deal. Buy the VRP then grab the premium pack (or one of the cheaper packs) via the store when discounts are on (like now).