I would reccomend:
Mouse: G400 - $50 (Wow that went way up in price)
Keyboard: Any mech keyboard for $100 will do, if you don't know what switch to get I would go for this: http://www.wasdkeyboards.com/index.php/products/sampler-kit-1.html
Mousepad: I would recommend the PureTrak talent - $25
Headphones: ATH-AD 700 - $100
Microphone: Zalman clip on ($10) OR if you can spare the money a modmic is an amazing mic ($30)
Total - $285
Or if you get the modmic it would be $305 or so