Let me provide an overview of my suggestions. There are literally books written about these topics, so the more you want to delve into leaning, the more information you'll find, and the better beer you'll be able to brew.
Fresh ingredients.
Use malt as close to being milled as reasonably possible.
Avoid old malt extract, especially liquid.
Keep hops cold and reduce air exposure.
Fermentation temperature control.
Any number of things from a simple water bath to a glycol jacket are helpful for keeping the fermenting beer in the right range to minimize off-flavors. A "temperature controller" thermostat is needed for the more advanced options, such as an inkbird 308.
Healthy fermentation.
Making a starter is relatively easy. Use a pitch rate calculator like the one from Brewer's Friend
https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/
Basically you make a mini batch of beer using dry malt extract at 100g/L, somewhere around 0.5 to 2 liters. A stir plate is very helpful to continually aerate, which improves cell growth.
Personally I make "vitality starters" which is 500mL, spun on a stir plate for only 4 hours before pitching.
There is also pre-made starter wort you can buy if you feel so inclined.
There are certainly a variety of other processes people use as well.
Proper wort aeration when pitching can be accomplished by a variety of methods from simply shaking the carboy to oxygen from an oxygen tank delivered directly.
I use a drill-powered stir tool and a tubing attachment that sprays the wort when I transfer it to my carboy.
Water and mash pH adjustments.
In my opinion, the path of least resistance and highest quality is to use reverse osmosis (RO) purified water from a local store, and add salts and acid/base from scratch. You need calcium chloride, calcium sulfate (gypsum), lactic acid liquid, and sodium bicarbonate (baking soda).
A calculator is needed to determine the approximate amount of acid or base needed to get your mash pH into the ideal range (5.2-5.6). I like BrunWater (free version), but there certainly are other options.
Determine your preferred calcium, sulfate, and chloride levels for the particular style, and then determine the amount of acid or base needed to adjust mash pH.
There is also a low-tech option for starting with RO water. Read more here:
https://www.homebrewtalk.com/forum/threads/a-brewing-water-chemistry-primer.198460/
Oxidation prevention.
In my opinion this is the second most important aspect of brewing after sanitation, and failure in this regard is likely the cause of the "homebrew" taste. Remove as many points of potential oxygen exposure as possible after the start of fermentation.
See
here for a post where I was helping someone who bottles.
Cheers