This isn't really a noob topic lol. Most people even with extensive history in playing/writing music don't end up looking too hard at the very technical side that you're talking about here.
Even then, I'm not really sure what your question is. Are you asking where the subdominant tends to want to go? And then are you referring to the note or movement into the subdominant chord from a key of c?
A lot of this stuff has really to do more with the mathematical relationship between notes. For instance, the reason why 'octaves' are the same note is that going an octave above a specific note only doubles its frequency:
"For example, if one note has a frequency of 440 Hz, the note an octave above it is at 880 Hz, and the note an octave below is at 220 Hz."
In the same sense, you have a sort of "shared importance" between the subdominant and dominant because the "[subdominant] is the same distance "below" the tonic as the dominant is above the tonic". Which means between the two they form the closest thing to the middle of that scale as you can get. Our brains tend to like things with mathematical relations which is why harmonics sound so nice. Musical components with no detectable relationship (say introducing microtuning halfway through a normal song) typically would sound horrible because there is proportionate relationship between the notes.
The concept of building tension and instability is a lot about how our ears relate a certain pitch to the tonic pitch.
Having a pitch that is 'unstable' doesn't mean you can't use it as a kind of anchor for a specific arpeggio. And here's where things in terms of composition become more interesting. Take an arp on a keyboard of C - E - G - B. Playing this over and over again against say a "C" in the left hand to solidify the tonic you would think would be grating but in fact it really quite beautiful. Then lower the tonic to "A" in the left hand while playing the same arp and the effect is similar even though now your "B" that your playing in the right hand is the supertonic which is also supposed to be very unstable. Let's say in either case you resolve the "B" in the arpeggio to a "C". The contrast is that now the arpeggio sounds boring. Strange right?
The trick to most very effective composition is learning to rely on inherently unstable notes and chord transitions to craft movement that keeps the listener expectant.