Hello Svro,
First of all welcome to PC master race. The PC your about to have will run for 6yrs but as yrs pass by new games require better hardware so at some point like in 8yrs+ your PC will be minimum system specs for a game. You have 2 options to chose from go AMD or INTEL, amd is cheaper than intel and will do the same thing but some games run better on intel. I have both AMD and Intel some games run better on AMD and some on Intel, most of all Intel+NVIDA wins.
Lets begin:
CPU: choices: i5 series, within these you have different models (http://www.intel.com/products/processor_number/eng/about/core.htm) any 1 would suffice but if you want little more FPS and can afford better cooling go for K series also depends if Mobo supports
Or AMD series from fx6000 or fx8000 select the latest ones
GPU: choices: AMD R9 270X/ R9 280/ R9 290X
NVIDIA GTX 770/ 780 (or Ti version) / 970 / 980 (or Ti)
RAM: 8GB frequecy and channel depends on Mobo. refer Mobo tech details for exmaple, dual channel and 1086 Mhz to 2100Mhz then get 2 Rams and pick frequency of 1333Mhx or 16000Mhz
Mobo: again which CPU u selected intel or AMD . Then match the socket of CPU and MoBo for example AM3+ for AMD cpus only, LGA1055 for specific 1055 intel cpu.
PSU: use PSU calculator
https://www.google.co.uk/search?q=psu+calculator&oq=psu+cal&aqs=chrome.0.69i59j0j69i57j0l3.1944j0j7&sourceid=chrome&es_sm=122&ie=UTF-8
I used cheap PSU for my AMD phoenix ii4 965BE overclocked its still alive for 4yrs. Maybe I was lucky.
Case: this depends on your Mobo, size: ATX mATX or uATX. Even cheapest one would suffice but make sure it has good air cooling or if your going for liquid cooling make sure it has space for it. Refer the youtube for how its looks IRL.
Visit Websites like Newegg, Scan, dabs, AriaPC, many others. Make a PC give it a trial, see what suits you. can u afford it and if you think this is the one consult here again.
Sorry for being very advanced but this is what you need to know when your building a PC for the first time.