soil is more forgiving, if you mess up in hydro your crop can die overnight, soil takes a few days to a week before symptoms occur.
before you go spending $2000 on a grow room, try to grow one or two plants successfully, this will give you a feel for how cannabis grows and its daily needs.
focus mainly on three things:
light: buy sufficent lighting for flowering a good 600wt HPS system will include a ballast, reflector, bulb, socket, and wiring.
air: you need a fan that can exhuast your grow room in five minutes, fans are rated in CFM (cubic feet per minute) so find the volume of your grow area (lenght x width x height) and buy an adaquate fan
nutrients: i like Canna nutrients, but there are all sorts of great nutrients, out there. just be aware some soils already have nutreints, you may want to avoid those soils and plant in soilless mix which has no nutrients, allowing you to control the amount of nutrients your plants get and when they get them.
aside from that there are thousands of things you can buy to make your grow more efficient or high tech. but you can start with stuff thats probably laying around your house and build onto what you have slowly. some things that are invaluable are
a good light.
a good fan
nutrients
ph meter
tds meter
bleach- keep everything as clean as possible, use bleach to kill bacteria and fungus BETWEEN grows.
a good timer that can handle your light wattage
and a good book on growing.
good luck