Hi there! Congratulations for diving into the "hardcore sim crowd "
Before bying any game i suppose you have a decent ff wheel ? like a g25 or a fanatek 911 turbo ? If not buy one the above first.The g27 is better then the g25 but you can find the g25 dirt cheap nowdays.
Forget about Iracing !!! Completely !!! Really i am not joking.It has some great open car/gtr car physics and some great online races but for the moment the amount of money you have to spend its ridiculus and there are very few not oval decent tracks out there.
Go buy a Gtr Evo/Race on combo.(You can install both games to merge all their content together).On a gaming pc the game will look much much crisper and will be silky smooth compared to race pro for x360....Also there are a ton of additional tracks to download.
Rfactor is basically a no brainer.Just buy the game retail or from the net.Add the real feel patch and then go to rfactorcentral and choose the top car mods/tracks to download.There are many very very high quality cars and tracks.From norchleife to isle of man,mount panorama,le mans,rouen,macau,magny course,barcelona,laguna seca,oran park,valencia,silvestone,lienz,eastern creek,sepang,suzuka,tsukuba,brands hands,fugi,detroit to the...70 mile targa florio....
And for cars...You can have normal real life cars like a supra,skyline gtr,silvia's,corvettes,lexus,ferraries,porsches,civics,integras,nsx,bmw's etc....
Or you can have Gtr cars like historic gtr cars,touring cars,american gtr's,supercar gtr's etc...
Or f1 like CTDP 2006-2009 or FSONE...
Also don't forget to give a look at LFS.It does not have a lot of content but what there is is incredible.You can have some incredible races in lfs .