While you are learning, you may find that the AI is much too fast for you to race with, particularly if you are not running with a full field of AI cars. In my humble opinion, the lack of an AI strength slider, or some way of allowing the player to adjust the AI's speed from within GPL's user interface is the single biggest flaw in an otherwise generally brilliant design.
Fortunately, there is now a utility, known as AI Tweaker, which provides a slick Windows-based interface to the various initialization file parameters which control the speed of GPL's AI cars. With this utiliity, you can control the speed of GPL's AI cars so you can race with them while you learn, even if you do not have the talent of a Jim Clark or a Dan Gurney. AI Tweaker was written by Kari Ikonen and can be downloaded from The Pits.
Note: if you can't get to the US server for The Pits, try here. This is the Norway server for The Pits.
To help understand the parameters which AI Tweaker allows you to adjust, I suggest you read the AI drivers section in my GPL FAQ.
If you prefer to manipulate the ini files by hand, you can download some files which I revised to make the AI easier to race with.
With the right adjustments, you may well be able to win races against the AI in short order.