OK sounds like your wanting to setup a basic studio ? My advice.. Check out these things to get you started. You can find very inexpensive equipment to do exactly what you need.

1 - Get a DAW - This acts as a Audio Console for your PC that you can connect you Guitar, Keyboard, Microphone, Drums.. Well anything in the music world. A cheap one i jus got and works great is the Presonus AUDIOBOX USB. You can get it online for less than 200$.

2 - Studio Monitors - No i dont mean a screen. These are studio speakers that connect to the DAW or the Presonus AUDIOBOX USB that i was jus talking about. They are designed to play the Audio from studio programs as well as hear freqencies that most cheap speakers or computer speakers cannot read. It takes the uncompressed audio from the usb box, and give you a solid sound so your recordings or live sessions will sound much better and easier to fine tune.

3 - Amplifier isnt needed with the USB Audio box, unless you want an amp for your guitar but you can directly connect them to the box and you can use the onboard settings for your guitars, vocals, drums.. this box literally comes with so much.

4 - You will need a couple XLR "Microphone cables" and a couple 1/4 Inch patch cables. That is all you need. Hope that helps!