My personal setup: Monitor: Benq XL2411T as primary monitor & old 17" Dell monitor for extended desktop, Keyboard: Filco Majestouch 2 Ninja Tenkeyless (MX Red Switches), Mouse: Roccat Kova+.
This doesn't mean that I think these are the best peripherals, they suit my personal needs. I chose a 144hz monitor because I enjoy smooth gameplay and the extra advantage in FPS games, I chose a mechanical keyboard because I want something durable and satisfying to use, I chose the Roccat mouse because I bought a Razer Deathadder previously and it didn't really fit my hand wheras the Roccat Kova+ fits just right. At the end of the day, only you can decide what you need from your setup. I personally would recommend you try different mice and keyboards with different switches if you can. If not then read as much info and educate yourself so you can make a better informed decision. Also you didn't mention your budget so I don't know if you can afford premium peripherals, but of course budget plays a big role in the choice you make. As for speakers, I listen to music, watch TV and play games on my system and I chose Edifier bookshelf speakers and they were only £60 off amazon and sound the same as my mates £150 hi-fi speakers. Highly recommended speakers for value for money and sound quality.
I hope this was helpful. Best of luck with choosing your bits. Have fun, it is exciting!!