You can only learn to race against people by racing against people
If you are a bit nervous of causing havoc at the start, spectate until the grid is formed and then join, you will be placed at the very back of the field.
You will learn more from spectating the fast guys than you will by trying to imrove on your own, and I know that I pick up a lot of speed on unfamiliar combos by chasing the faster guys.
Don't worry about ruining peoples races, as long as it is unintentional and you apologise and don't generally act like a muppet then you would be welcome on any server. Also, if you let the racers online know that you are new, you might get a little tuition for free