To me, it's not about what gear you have, but instead your ears, your mind, and how you use them
I tend to focus more on principles than on a specific "hey twist this knob this way to fix that thing problem you're hearing.
Here are two principles that you can apply to your recordings today....
the Frequency spectrum and striking a balance.
this is one of the early stages of mixing anything with more than a single track. Imagine that graph from 20 Hz to 20kHz which instruments fit into which areas?
hint. these questions can be answered with the help of an equalizer.
Sonic density and energy
This part usually becomes more of a concern towards the end of a mix. after everything is in balance. Imagine that bass guitar that is covering your kick drum. is there a way to make them not interfere down in the deep low end? Why do my vocals sound so Thin and tinny while my guitars sound big and full?
yes. it is a question about frequency, density and energy. Each track has its place along the frequency spectrum, sometimes there is overlap. the bottom end of your guitars overlapping with your vocal, the bass with the kick drum, guitars recorded using half-a-dozen tracks while the vocals used only an SM57 (microphone for all you total newbies reading this)
Now, there are two options as far as density is concerned, More or Less? that's it. Remember we're talking principles here, not gear.
lets look at some STems
Lets say you're recording some folk rock with a punk-rock influence... you've got some Guitar Bass and Drums Are present but not overpowering but it has that dirty-rock feel of distortion and quite a lot going on sonically.
Guitars - these are the focal instrument of the song. notice the amount in power in the higher frequencies... That's where the distortion is living.
Bass - This bassline has quite a bit of 'density' compared to a lot of the other tracks but note how there is really nothing going on up in the higher frequencies (above 5kHz) It was purposefully removed, nothing useful up there.
Drums - a real drum-kit will be noticeable across the entire frequency spectrum.
These tracks were recorded and mixed to cut through where they needed to in order to sound clear and balanced. common areas of conflict in drums are