what are the 2 or three must have racing sims on the pc and why. im just starting out and im kind of lost as to what to buy thanks for your advice

From my european POV : iRacing (haven't raced it but highest realism ever), rFactor (cheap, easiest of the true race sim, lots of mods), rFactor 2 (haven't raced it, still in beta but already seems to be a must-have)

Oh, and as a big fan of Grand Prix Legends I have to mention it

Hmmm lets see

iRacing Its a monthly subscription online racing only sim. However it is the most realistic racing Sim on the market today.
RFactor 1/2 Rfactor 2 is in Beta and will be out soon. The Rfactor series is arguably the most modable racing sim.
Project C.A.R.S Not even in its alpha state yet but is an amazing visual sim. The racing isnt bad either!

Right now you could pay for iRacing and only play it as long as you keep paying for it... But it is the best of the old gen by most accounts... I'm not willing to pay a monthly sub for a game so I don't know...

Or you can go the old rFactor or GTR2 route and go for the free mods that have made those games so popular...

Or bide your time for the raft of next sims that are in development at this point in time...

rFactor 2 has the potential to make the last gen seem irrelevant, pCARS is stunning visually and is a little less serious on the physics... Simraceway has a interesting model where you only pay for the cars you want to drive but is based on improving the last gen... All 3 can be bought into right now to become part of the BETA testing phase...

And then there's GTR3 and Assetto Corsa both are highly anticipated... But are both closed BETA...

For me it is:
Rfactor
GP legends
Race07

Grand Prix Legends because the physics are still amazing, there are great mods for it and hundreds and hundreds of tracks, all free. It is a time machine and and offers single player with immersive and good AI as well as online play.

Richard Burns Rally because it is the GPL of Rallying. Very challenging.

iRacing because it is made by the guys and gals who made GPL.

GTR2 because it is Simbins finest to date, with plenty of mods.

rFactor, as mentioned has innumerable mods.

Hmm, as much as I love GPL it cam definitely be described as in at the deep end.
If your up to the challenge though Google
Grand Prix Legends 2004 Demo
You should find loads of places to download it.
Its fully functional and updated but only comes with one of the original track, Watkins Glen.
All of the hundreds of add on tracks out there will work with it though so you'll barely miss the originals.

Before recommending iRacing, it's important to ask the person if they want a 99% online MP experience. It's a racing career simulator, played with other people simulating their careers. Races can't be paused.
If you're in an environment where you can sit uninterrupted to run races on a schedule not your own, then it's certainly worth at least the discounted trial subscription.

Can't recommend GTR2 for practical reasons. I've never gotten it since I couldn't find a copy for under $100 (I won't buy a pc game used). Race 07/GTR Evo is worth it though.

rFactor if you're comfortable downloading and modding, otherwise it's worthless. There is a TON of content out there ripe for the downloading though.

hummm.. there seems to have some under 30$

Ebay GTR2 link

I have NEVER seen it listed like that before, new, on Ebay or elsewhere. Looks like I might finally end up with it, thanks for the link.