Hey man, I am just starting and just joined the forum as well.
Do what I did, use the search function and type in something like “new karter” or “newbie” and you’ll see alot of people have asked the same thing, and the past posts are very informative.
As far as 2 stroke and 4 stroke, 4 stroke is more reliable but more expensive. 2 stroke require a little more maintenance but more people run them.
As far as racing goes, there are club races that take place between IMI and The Track at Centennial. If you are close to IMI, The Track at Centennial should be roughly an hour from you. Those are basically recreational races. You’ll hear alot about a series called Rmax, which is considered to me at a more national level, and if you want to run in that series you must run a Rotax motor. As far as the club races go, you can use any brand motor. But I believe the 2-stroke and 4-strokes run separate classes.
If you are close to IMI, there is a race going on there this weekend. Everyone will tell you to go down there and talk to ppl and ask questions. As I said I just started and everyone here has been extremely helpful.
Thats the little that I know so far, hope it helps. I’m sure some other members will chime in shortly :cheers: