I recently sold my rig (which I dearly loved but must sell) and what I had included:
Logitech G300 mouse; I don't know if they sell it anymore but it's AMAZING. Custom lights (for different mouse settings), multiple buttons, feels GREAT, smooth.. I used it to play CS:GO & Dota 2 and I would switch the settings by hitting one of the buttons when I played either game (I set different dpi etc. for each game).
Keyboard: I had a Steel Series Merc Stealth.. It's a great budget board for under $40 but I'd highly recommend a mechanical keyboard.
Headset: Do NOT buy gaming headsets! Seriously, buy a nice good pair of headphones and a Zalmon clip-on mic.. the quality is so much better for the money you're spending. I bought some Sony MDR-X10 headphones (on sale) with a zalman and it was so much better over the Turtlebeach P11's/X12's I've owned but returned because the quality was horrible. For the headphones, I wouldn't necessarily go with the one I have but do some extensive research and you'll find a nice deal.
Monitor: I had an Asus 23.6" 247H-P monitor and it was excellent. Got it for $135 because it fit my requirements of 1080p, 5ms response time, hdmi ports, etc. I'd highly recommend Asus monitors.