You can buy a usb audio interface for your computer. There are several good ones and they usually come with digital audio workstation (DAW) software such as ableton or cubase or some other DAW.

For guitar playing, just plug your guitar directly into the audio interface (they usually have 2 inputs).

The nice thing is that when you learn to use your DAW, you can lay down a track with your guitar, then play it back in your headphones and sing into a mic connected to the same interface.

This would help you by you being able to cheaply record, while allowing multiple tracks and making changes or recording over a rough part.

The DAW will usually come with a few effects and before you know it, you are just creating once you get the workflow figured out.

A good place to start your research is with the Focusrite Scarlett Solo (2nd Generation) USB Audio Interface. You just have to find the right features for your needs and your pocketbook.