as garden known says...if u go cheap u grow cheap...or soemthing like that...if u throw together a grow room cheaply then chances are ur plants arent going to be as good of a quality is if u use the right products

theres alot u need to buy

pots
soil/perlite
nutrients
bottled water? if u use it ( i just let tap water sit out for a day)
light bulb
electric cost
seeds/clones
fans
ac/heater if u need 1
exsaust
ventialiation
wiring/ballasts and all that stuff for lighting
ph tester and thermometer
mylar or white paint...

ect...it isnt cheap