1) Get a good enough computer to run CS:GO. At least an Intel i5 processor, good enough gfx card, 8gb ram and if u have the budget then a 120/144hz monitor. You need at least 200-250+ fps to enjoy/play the game properly.
2) Selecting the equipment you play with (mouse , keyboard , headphones) . It's all personal preference, manufacturing companies make mice with 10,000 dpi and so on which is just a marketing gimmick. Mostly people use 400-2000 dpi so only select a mouse that suits your hand best.
3) Ingame settings, resolutions and all that are personal preference, use what suits you best. Of course if you don't have a good enough pc to run CS:GO then you have to play on lower resolutions to make the game run smoothly.
4) Once you are done setting up everything, it's time to play and take the feel if everything is as you desire. Start off with playing on some pub servers or death-match servers. Playing on DM servers will improve your reactions and also make you familiar with different guns and their recoil and how to effectively use them.
5) Once you are familiar with the guns and overall game mechanics then it's time to play competitive mode. Competitive mode is the mode which is played in tournaments and higher level , basically its 5 vs 5.
6) You can play 5 vs 5 on valve official servers or on other platforms like ESEA ,FACEIT, SOSTRONK and so on. Valve servers are 64 tick rate servers, while other platforms offer 128 tickrate servers which is desirable for real competitive matches.
7) Once you have played competitive mode and are familiar with the game and different maps , then you can go ahead and watch demos of pro matches. You get to learn how professional players play and what type of approach they have in different maps and scenarios. Most pro players have been playing since many years and have evolved as a player so it's easy for us to watch their demos and learn quickly.
8) Now that you have become a good individual player, it's time to join a clan/team, or make your own. You should practise with your team and come up with strategies on how you will play or look for similar style pro teams and try to adopt their strategies.
9) Playing together with your teammates enables you to understand their play-style and how they play so that you guys can coordinate and play as a team. Try playing against better teams than your own, you might lose a lot of times but that's how you get to know your mistakes and get better.
10) There are different game modes to improve your movements and reactions in game. To improve your movements you can play surf maps and to improve your aim/reactions you can play on different custom made maps against bots.
11) When you are ready with everything, here's a basic formation of a team. Usually there is 1 ingame leader who commands/leads the team and decides what strategies to use at which given point, 1 sniper who is better with scoped rifles, 1 entry fragger who has great aim and fast reflexes (he usually enters first then his team follows him), 1 lurker who is very patient and understands when to take advantage of situations, 1 play-maker who is experienced and good with clutching the rounds and lastly 1 support player who helps his teammates with setting up smokes and flashes so that his mates can capitalize on that.