I have been on iRacing for over 5 years. For the best experience, I would highly recommend joining a league. With a league, you generally race with the same people be it nightly, weekly, whatever. With this comes more respect from other drivers which leads to cleaner racing than with total strangers in official races.

You can spend as little or as much as you want on iRacing. If you are just starting out and don't want to invest a lot of money into it I would recommend finding a Logitech Driving Force GT. If you want to spend a little more, go with a Logitech G27 or G29 as others have suggested. The iRacing forums have a lot of information, especially in the Hardware section about other options if you feel like upgrading in the future. The resell value on sim racing equipment is pretty high and items tend to sell pretty fast on the forums is you ever decide it's not for you.

If you have any questions, feel free to reach out.