CS:GO is very popular, after playing about 200 hours on this at this point, these are my findings:

There is a lot of fun on this game and many teammates to find.
I started with casual just to get into how to play this game because i was new to it.
I recommend to do the training course first and find some maps on the steam workshop where you can practice your aim and understand the spray patterns of each weapon.
I overall enjoy competitive more than any other gamemode, because it makes you play the game better and gives you more experience overall which gives you the ability to learn from your mistakes and improve more and more, at least that are my findings after more than 50 competitive matches. You will see that communication will be the most important thing in competitive, teams who don't communicate are most of the time useless!!!

Why should you buy it?

Simply because it's a fun game.
It gives a challenge to yourself to compare and measure with other players or to meet people and become great teams who get to know eachothers playstyle.
The gamemodes and competitive is fun, it's nice to collect skins or to use other people's weapons.
You get to practice your skill more and more.

What to do to become better at this game?

PRACTICE PRACTICE PRACTICE! Thats the best way to learn this game.
After a while you get familiar with the maps and the perfect spots to either attack or defend.
Get to know the positions in the maps, so you can call them out when there are players.

Bad things about CS:GO:

Every day i get to see someone who uses aimhacks or wallhacks, which is very frustrating and annoying... the chance of winning is 35% i'd say.
There is a lack of good matchmaking - what i mean by that is that sometimes there is one really big noob team which is useless against better players.
It is annoying if the team doesn't communicate, it makes the game boring,also the CS:GO experience becomes less amusing.
Competitive is certainly not for you if you are a ragequitter, because you'll get a competitive cooldown. After a while it goes up to 1 week and more.
Low levels can play just a few matches before receiving a 24h cooldown due to no rank yet.

CS:GO is very popular, after playing about 200 hours on this at this point, these are my findings: There is a lot of fun on this game and many teammates to find. I started with casual just to get into how to play this game because i was new to it. I recommend to do the training course first and find some maps on the steam workshop where you can practice your aim and understand the spray patterns of each weapon. I overall enjoy competitive more than any other gamemode, because it makes you play the game better and gives you more experience overall which gives you the ability to learn from your mistakes and improve more and more, at least that are my findings after more than 50 competitive matches. You will see that communication will be the most important thing in competitive, teams who don't communicate are most of the time useless!!! Why should you buy it? Simply because it's a fun game. It gives a challenge to yourself to compare and measure with other players or to meet people and become great teams who get to know eachothers playstyle. The gamemodes and competitive is fun, it's nice to collect skins or to use other people's weapons. You get to practice your skill more and more. What to do to become better at this game? PRACTICE PRACTICE PRACTICE! Thats the best way to learn this game. After a while you get familiar with the maps and the perfect spots to either attack or defend. Get to know the positions in the maps, so you can call them out when there are players. Bad things about CS:GO: Every day i get to see someone who uses aimhacks or wallhacks, which is very frustrating and annoying... the chance of winning is 35% i'd say. There is a lack of good matchmaking - what i mean by that is that sometimes there is one really big noob team which is useless against better players. It is annoying if the team doesn't communicate, it makes the game boring,also the CS:GO experience becomes less amusing. Competitive is certainly not for you if you are a ragequitter, because you'll get a competitive cooldown. After a while it goes up to 1 week and more. Low levels can play just a few matches before receiving a 24h cooldown due to no rank yet.