All of them, really. You can't take shortcuts if you want to be a decent speaker of any language.

Depends of how fluent in English you wanna sound. Cuz if you only use "will" for future, simple past and simple present, you may not express exactly what you are thinking, and you may not be comprehended. There are subtle, yet crucial, differences from the simple present to the present continuous, from "would" and "should", etc. The more you know the best it is for you.

Present, past, and future tense are the most common. (I visit Russia. I visited Russia. I will visit Russia.)

present simple