I'd like to add that depending on the game or game type, you might want to also incorporate "drills". It's easier to practice some things when not under pressure or overwhelmed by lots of decision making.
Edit: Drill should be like... If you play 7 days a week, have about an hour to an hour and a half of drills a week. Pulled these estimates out of my ass kinda, butt the general consensus is you should play way more than you do drills. Kinda like when practicing sports, I imagine
For example, if you're thinking of playing FPS games, they there's great aim drills for aiming techniques (flicks, tracking, microflicks, pre aiming, crosshair discipline, etc) in Kovaaks. But then you also gotta think about movement (long peeks, short peeks, dodges, strafes, etc) and positioning (corners, high ground) that are best practiced in game.
For mmorpgs it's all about positioning, cues and your practicing rotation timings (instead of aim drills) and counters. Understanding how buffs and debufs stack and interact. Movement can be important and a bit of meta gaming too
Also gotta think at a little meta (how does the game process input and animations, animatio cancels) for really competitive levels.
I would say mechanical skill is usually 20% and the 80% is understanding when and where to be, and what to do; only then does mechanical skill matter. If you are out of position and have great mechanical skills, you will get punished before you can utilise your aim/rotation to their fullest potential, but with good positioning (ie cover, staying at the edge of range, highground control) gives you more opportunities to execute if your mechanical skill fails you.
Speaking of mechanical skills, step 0 is setting up a comfortable, ergonomic workspace to play. If you're going to be spending a lot of time on any task, you want to make sure it's not going to wreck your body. PC gaming is easy ergonomically, because we know how to setup an ergonomic computer workstation, but pay a bit more attention to the mouse. Console gaming, you can setup like a computer workstation, and put the controller where it's comfortable. Or do a traditional tv + couch setup, but at least make sure the heights of things are good.
Step 2: play video games that reward deliberate practice and skill
Step 3: put in effort on reducing lag, especially if you're playing games developed in the time of CRTs. Modern games are built and tested with modern everything and you get more time to react to things, but games built for CRTs expect nothing more than a couple gate delays between the video out and the electron beam, and for the inputs to be current when sampled. Modern displays have a lot of nice things (convergence is great, vertical and horizontal alignment is perfect, the picture size doesn't change when the background gets brighter or darker, etc), but they usually also have an image processing pipeline that's measured in milliseconds, some take much longer than others. Bluetooth controls use bluetooth, enough said.
Wired controllers and a CRT won't make you good, but flakey wireless and a laggy LCD might make you bad.
Step 4: make a practice plan and use it, and adapt it as necessary.