Notes on paper:
First: Clones can perform various attacks all at the same time. Indeed, imagine if you had three clones in front of you all release different jutsus at you at the exact moment. It's like breaking time frame.
Second: It is hard to tell the difference between the real you and clones. Only the Sharingan is able to tell such differences, or normally, people just godmode this in battle.
Third: Being able to combo greatly with split-second jutsus - imagine seeing several attacks coming at you at all directions.
Fourth: Distraction in general - for example, a clone used Thunder Up, and caused an explosion, the enemy will be drawn to the noise and you could then take advantage of this.
Fifth: Release of Genjutsu.
Sixth: Sacrifice for information.
Seventh: Increase of field of vision. Blind spots.
Eight: Human Shield.