So one of the most important rules is to fix it as early as possible in the process. Starting from the beginning (that is to say, none of this is specifically tailored to your specific songs yet)
1. Write great songs - If your songs aren't worth recording, fixing it in post won't be worth it. Make sure your songs are as well-written and well-arranged as you can make them.
2. Get great performers - Make sure your
performance when playing is perfect (i.e. that your
performance exactly matches what you want out of the project.)
3. Track with good gear - Make sure your instruments have exactly the tone you want.
4. Track in a good space - Make sure that background noise, reverberations in the room, etc. aren't going to interfere with your sound.
5. Track with the right mic - The right mic being the one that most accurately captures the sound of your amazing
performance using great gear in a good space.
6. Mix it right - That's what this forum is for! Whee!
7. Master it - I'm far from
expert here. Talk to massive mastering once you reach this point.
As to your recordings specifically.
The major spots I can see to improve right away are:
Tune
the acoustic. It's got some pitch issues, especially in "Search for a Spark"
Tame the low-end. Your kick especially is pretty woofy. Bass traps in your room will keep those frequencies from building up while you track. When you mix, look into low-pass filters.
Level out the vocals. You've got a few spots where the vocal level jumps up or down drastically, being buried one moment and too loud the next (especially on the gang vocals). Use automation and compression when you're mixing to keep things coherent.
Find a space for each "voice" in the mix. Each instrument (voice) has its own set of frequencies that it works best in. You want to EQ voices so that they're not trampling over each others' preferred frequencies. This will keep your mix from getting muddy.
That being said, a couple of your songs are pretty good! Your vocal delivery is a lot like MC Frontalot's in a few spots. When the mix clicks, you've got a pretty solid groove. I like the rap/acoustic/synth sound. And from what I was able to catch, you've got some pretty good lyrics.
Your singing voice is a little weak. You might want to get someone to help you with the hooks. (Unfortunately, there's not a ton of love for rap on these forums, so you might not be able to find a ton of collaborators here)