for the mouse the steelseries world of warcraft cataclym mouse is perfect for games u have 12 more butten and u can give the buttons keybindings so it can be used for every game. for keyboard i dunno im using a normal keyboard dont see the need for a new one and as an headset any headset with a mic thats wired is good but i would personally look for a headset with a good range of Hz like between 20Hz and 20KHz i would personally think its best.
Right now im using a normal 10 year old keyboard and i must say it's very good and im not going to buy a new one until it dies.
The need for a "gaming" headset is highly debatable as ive used both a "gaming" and a "audiophile" headset and i like the second one better.
But you absolutely need a mouse.And you need a good one.
As an very experienced razer user, i wouldent recommend you buying the Mamba, its fanct and all that, but it sucks to hold in your hand. The best mouse from Razer is the "Deathadder" . "AND DON'T BUY THE BLACKWIDOW" My old blackwidow ignited a lighter in my room while i was sleeping, i could have been dead if my friend wasent awake. Now you might think, "whaaaat" but this happed to his keyboard aswell, i saw it with my own eyes. + don't use razer store, their customer support is terrible