I have a Cybertron gaming computer but it's running behind on games. What do I need?

As I said, I need to find some software for my computer. It's a legit gaming computer, but I can't seem to play games that I should. I was promised to be able to play top notch games (The newest) till at least 2016. I know it's pretty close, but it's been going on for months! Like The Ark: Evolution Evolved, as an example, I have to turn the graphics down to bare minimal and it still lags like hell. That is just one game. Minecraft, The Forest, League of Legends, Starcraft 2, World of Warcraft, and more are not working at the best if their capabilities like promised. Now I asked Best But about it, but they just gave me a list of stuff for me to buy, of course -.- . Now I know I'm gonna need to buy stuff, but if anyonne can tell me EXACTLY what I need to buy or do to my computer to make sure it can play games up to date perfectly and smoothly, that would be lovely. I'm starting up a youtube channel and I wanna try to get an edge. Been planing this for three years, I don't want to have my lack of technological knowledge prevent me from starting up my channel.