Hi, I haven't played sc2 in such a long time (I think I stopped the moment master league was introduced).
At that stage, I was a platinum, but a big reason was that I would only
1) Cheese
2) follow one build

Since I don't wish to follow those same footsteps again and instead IMPROVE...

how should I go about doing this?

1) Should I stick to one race? Or go for random? (I'm Korean if you are asking, but I don't think I can play zerg effectively, lol).
2) Should I be first getting really good at ONE build, then branch out to different ones the moment I can play the aforementioned build perfectly?)
3) Should I be warming up/playing any custom maps?
4) Would watching pro streams help? Or is the gameplay at high levels too different from lower ones?
5) Any other advice right here please!

we arent asking. Practice one opener for each matchup for each map in the ladder map pool. React to what your opponent does. Most important thing is to actually play, dont waste time watching streams or tournaments unless its for enjoyment. you wont actually get better without playing.

Pick a race you like. Ladder lots. Do 1base all ins until you feel comfortable with those timings. Then do standard expand builds until you're comfortable with those. With the expand builds, work on doing 2b timings. Then you can decide if you want to learn to 3b macro or do 2b all ins.

Keep it simple. Don't do super fancy shit, like protoss air openers. Don't get too mad when you lose.

Watch pro streams when you can so you pick up the metagame, standard builds, how to react to various situations.

The most important thing is to just play though.

watch day9 dailies religiously. especially the newbie tueday videos

Any BW experience?

No not really.

then not a real korean sorry.

csb

Try not to have an opinion on balance until you get to at least masters too, that pisses off a lot of people here.

Ofc. Balance talk should be restricted only to those in well-versed in the game.