I can give you some tips on buying a PC and the basics of what a PC consist of.
Your first choice for the common gamer who don't know anything about building PC's is to pick a PC with the word "GAMING" on it. In my experience you get a lot of extra features like over-clocking and other fancy tweaks that you will never fully use and if the PC has a fancy brand name it is often over-priced like with the Apple IPhone etc. It works as intended but you pay extra for the fancy package.
Your second choice is to build a PC from components you pick from a web store where they might provide a "PC builder tool". You pick and chose the part's and they guarantee they work together and they assemble your "custom" PC and make sure it works before shipping. You probably won't have unlimited options but maybe more options than the "GAMING" PC setup.
Your third choice if you want to get your feet wet is to attempt to build your own PC. If it is your first time and your money is limited I strongly recommend you find a friend that knows what he is doing and get him to help you out the first time so you don't waste your hard earned money. That being said, it has never been more fool-proof than it is today, although there is limitless combinations and limitless bugs that may occur.
When it comes to brands in my experience there isn't that much of a difference anymore, as long as you don't buy some no-name brand made for china.
ASRock, ASUS, GIGABYTE and MSI are all good for gaming to name a few.
First you need to choose a Central Processing Unit (CPU)
(Recommended for PS2 is Intel i5 processor or higher / AMD Phenom II X6 or higher)
The CPU does all the calculations needed to run a Program/Game except Graphic's.
A slow CPU shows if your PC takes a long time to start-up or to begin a program/game or if the PC get's "stuck" briefly.
Secondly you need to choose a Graphics Processing Unit) GPU
(Recommended for PS2 is nVidia GeForce GTX 560 series or higher / AMD HD 6870 or higher)
The GPU is working with the Graphic's tasks so the CPU don't have to.
The GPU can be one or even two identical Graphic cards connected to the MB through a specific slot. Today's standard is PCIe v3.0
The Graphic Card comes with it's own designated RAM (Random-Access Memory)
(recommended 1GB total for PS2)
Thirdly you need to chose a Motherboard (MB)
The MB is the largest component in your PC, and there is several choices you need to make before picking one out.
1: What type of CPU socket do I need? (this depends on the CPU model you got)
2: How many SDRAM slot's does it have and is the total max RAM enough for me?
(8GB or more is recommended for PS2)
3: What type of PCI ports does it have and can my Graphic-Card Physically fit inside?
4: How many HDD (Hard Disk Drives) do I want to use including SSD (Solid State Drive)? and what standard do they use? SATA 1.5, 3, or 6
5: What does the IO shield offer? USB ports? etc.
Other notes to make about the MB the normal size is ATX which fit with a standard ATX tower Casing for example. ATX-e cases are a little bigger and makes it easier to fit in large graphic's cards, but it is normally not necessary.
Other things you need is a power supply, if it isn't included with the case. There are websites available to calculate how much power your pc needs but you should always go over by maybe 20% since PSU (power supply units) normally are very inefficient when above 80% load. Save the planet
My own rule of thumb for a gaming pc the cost of the components look like this.
25% GPU
20% CPU
15% MB
15% RAM
25% Other (PSU, HDD, SSD)
Casing, Screens, Fans, keyboard/mouse etc. not included. since they have no direct impact on performance.
I hope I didn't lose you completely through this wall of text, but you can always ask again or search YouTube for tutorials. Some of them are quite detailed.
