I'm trying to get into pc gaming, is a 2 core pc with 3ghz good enough?

It would be best to build your own. An intel i3 should suffice, but an AMD with a quad core would do too AMD is cheaper so you can get higher specs with that. Best to build your own PC to maximize your budget.

http://www.reddit.com/...r/buildapc is the best place for anything and everything with assembling yourself a pc. Its an extremely helpful community.

Performance is more then just "paper specs". This is because depending on the manufacturing process, the same numbers can mean VERY different things.

like intel and amd make cpus in VERY different ways. You can't just compare things like cores and clock speed and cache.

Really the only true way to compare performance, is to test it yourself. Or the next best thing is trust someone else to test it for you. Which many places online do benchmarks and reviews on pretty much everything. (YMMV, and ofc you always have to take it with a grain of salt. As they all use different testing methods, and some may even be payed off to favor one over another)

But still benchmarks, especially if you check many different sources, is a great way to determine performance of hardware you don't own to test for yourself.

Games like minecraft and CS;go are really not very demanding games. Running something like a pentium G3258 and a gtx750 would be more then enough. But id advise you not to completely center your build only around those games. As there may be games you have never heard of or played that you may like, and if you limit yourself to your hardware, then you will never be able to.

Id suggest getting something that can atleast "play" (meaning atleast low settings at 1920x1080 at a minimum of 30+ fps) all games available at the time.

for that something such as an i3-4150 or amd fx6300 and a mid range graphics card like an amd r9 270x should be great for. Should be able to build such a system for $600 or under pretty easily. (a system like this should be able to handle the witcher 3 on medium settings very well. Which is by far the most demanding game available atm)