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Be kind.

1) Observe your teammates buying behavior unless they force every round .
-> if they do force every round, ask for an eco round.

2.1) If no one in your team has above >4000$ but you have still >2000$ you can buy down to 2000, which is called a 2k buy.
-> suggest 2k buys if you spot a given chance.

2.2) If no one in your team has >4000$ but you still have >2000$ and you expect your enemie to have low money (due to spotted Forcebuys) or because they just lost a round after you won, you can suggest a Forcebuy.
-> try Forcebuy when given a chance or feeling comfortable.

3) Talk with your team.

4) If your whole team has good money (to buy utility/defuse-kit etc) do so, dont save up money for an AWP unless someone can drop you and is willing to do so!