Since we really can't command ourselves to do things, it is more of a suggestion along the lines of "Let's do something."
Using the Subjunctive form of the Nosotros adds emphasis to the suggestion.
The most common form of the Nosotros command is one we already know:
Vamos + a + Infinitive.
|Let's go to the park!||¡Vamos al parque!|
|Let's go study for 3 hours!||¡Vamos a estudiar por 3 horas!|
Or we can be a bit more emphatic and use the present tense Nosotros form of the Subjunctive:
|(Seriously) Let's really study for 3 hours!||¡Estudiemos por 3 horas!|
While you have a choice for a positive suggestion, you must use the Subjunctive form for the negative suggestion.
|No way! Let's not study for 3 hours!||¡No estudiemos por 3 horas!|
|Let's so not go to the park!||¡No vayamos al parque!|
So although you can avoid the Subjunctive with the Vamos + a + Infinitive for the affirmative suggestion, you will still need to know the Subjunctive in order to form the negative!
As with any Command form, if you use Direct or Indirect Object pronouns you must attach them to an affirmative command (and add an accent to preserve pronunciation) or place them in between the "no " and the command for a negative command.
|Let's buy it!||
[¡Vamos a comprarlo!]
|¡Let's not buy that for her!||¡No se lo compremos!|