build my grow room

i want to grow 3-4 plants. wat deminshions should i build it in? im doing a cfl grow im not sure if im going hydro or soil im confused by both. i understand that 6500 is for veg and 2600 is for flowering and if i use hydro im gunna use gh 3 part nutes nd its 100 watts for the first plant and 50 watts for each plant after that. i dont under stand how the ventilation works in a grow box all i know is that. on hole is for air to go in and the other hole is for it to go out throung a carbon filter.

u could go as small as 10 but remember small pot small plant