Ballasts and LED for gorilla tent.

Debating getting a Gorilla tent however I am super novice (in middle of first patio grow, 1seed and 5 clones) and noticed the tent comes as is so I will have to buy all other parts a la carte. I am interested in using LED due to apartment living and worried about heat. I do not understand the concept of ballasts.. Do I need a Ballast for LED lighting? Also, where would the ballast go? Outside or inside the tent? What strength LED (and/or any other lights) should I use for 3x3? Would a 600 watt MH or HPS be too strong for 3 x 3 x 7? Anybody have any suggestions as far as how to setup the tent regarding ballasts and lights?

Leds are fixtures not like hid lights. Onyx has a separate power supply. 3x3 either area 51, apache tech, or onyx bloom. Will be a lot easier to manage an led in that space over a 600w MH or HPS.