Ok so right now I would like to be able to record demos for my musical ideas and such and want to know how should I go about recording:
Right now I have a Fender Mustang 3 amp, so I will be able to record lead and rhythm guitars though the USB ports no problem
With the bass I plan on micing it and I have a tiny mixer, I'm guessing that would work
And for the drums I have a drum pad, but would need to know how to get a proper set up for it.
For this whih recording software would be good right now I have atleast $150 to spend
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Bass you can record direct, don't need to amp. Maybe it'll work with some clean settings via the Mustang.
For drums probably EZDrummer for the sounds, or one of the other drum plugins. Depending on your software you might have some vst synth sampler that has drums.
You should really think about investing in an audio interface, the Mustang is ok for getting audio into your PC but you are limited to 44.1Khz sample rate. With an audio interface you will be able to record two or more instruments at a time.

Audio interfaces come with free DAW software letting you get into recording, alternatively most DAW software has free versions (Studio one for example) giving you a taste of what you can expect from a full version should you wish to spend any cash.