how to get better on pc?

Positioning is key, don't rush in, try to get in a good position first before engaging in gunfights and know when to fall back.
Most of these things you learn with practicing but there are some videos that can help you with that.

What FPS are you aiming to have with which GPU/CPU? @NOSWOHL 

all your settings low, or off, anti aliasing on if you dont like the jagged lines,  110 fov if you have trouble seeing lower it, try going to 104, then 100, then 90, 90 you will be able to see people really well in front of you by nor to the sides too well, you want a lower sens, try 1.2 sens with .9 ads sens, also download aimlab its free on steam, try gridshot, and a tracking one, change the settings so its your apex settings. do the aim lab for 30-1 hr before you play

watch streams, watch albralelie, watch daltoosh, watch tsm imperialhal, watch any good streamer watch what they do and try to emulate it. think about where they are playing and why 

soon enough you will be plat, and playing vs those very people every game. have fun my friend

There really is no better substitute than just playing to be honest.

Have a large mousepad and lower sensitivity will help a lot, the guideline when it comes to sensitivity is to set DPI to a value on the table of 2, ergo, 800, 1600, 3200 etc. 800 is often used, and adjust you in game sensitivity so that you can comfortably make a 180° turnaround moving the mouse from the center of your pad to the edges.

Graphics settings is something most people dial down to lowest possible.