Unless you're a technophile who wants the latest upgrades to most any component, staying 3 years behind when purchasing NEW components saves you a lot of money.
Let's look at decent (off the shelf) machines from walk-in retail stores or puchases made online. Let's say you spent $1000.00 for an enthusiasts or gaming machine in 2009. That machine can be upgraded in many ways with components that were manufactured in 2010 to 2013 and not cost you nearly as much as something produced in 2014 and 2015.
A machine will last 7 to 10 years easily in terms of it's hardware configuration and how well you keep the inside of the box cleaned.
Here is how you begin. Use your search engine to look up "best reviewed atx motherboard 2012". Or "best reviewed cpu in 2012" etc.
Find the components and then go to the mfg's site and find what other components are recommend as being compatible.
I always start off with the motherboard since everything gets plugged into that main component.
Having the latest and greatest means thousands of dollars. Having something you build from scratch with NEW components that are three or four years old will cost you hundreds of dollars and will last you a very long time.
The idea is to build or upgrade your machine to the most demanding game you have installed. Those of us who play golf games such as Perfect Golf, Tiger Woods 2008 etc., need a beefy Video Card (2GB) with at least 4 to 8 GB of Memory. The CPU needs to be dual or quad with ea core above 2.5Ghz. (I recommend 3Ghz+ ea. core)
Always make sure you put a PSU (Power Supply Unit) into your machine that is 100 to 200 Watts above the demand of your video card, especially if you are running several HDD's and one or two SSD's.
