Ok man, dont take my post the wrong way as it may be alittle long but worth the read...
I start alittle over a yr ago with same type of posts as you. Didnt wanna spend a ton in equipment just to realize i needed more or different kinds. Figured id learn as i go but atleast the equipment was purchased correct the first time... there is a major issue with that...
Starters, everyone on here will give your THEIR way of growing and THEIR way of equipment/enviroment. This will not work for you. Each grower has heir own level of talent when it comes to this. They have their own attention to detail and ambition to be inside the room ALL the time. You need to do a run on your own with very small simple setup. You need to see what training you prefer to do and if your strain likes that training. You need to dial in a solid nute program with your strain. Some people can only be in the room once a day if that compared to someone being there everyday multiple times. You need to decide which you can do and then decide your system based off that. Then learn that system.
You need to stop and realize each individual plant even if the same cutting from same mom plant will grow at its own pace. This takes dedication and the ability to put your pride aside. Also, light may = wieght but only to a degree. Training, enviroment and food control is absolutly more important than having ton of light. A 9x12 room with 4-6 lights will be a pain to keep in good temps without enough money of fans ect. I could go on and on but i know your going to overlook this cause its basic info. Knowledge is nothing without experience.
IMO, get poly and make a small room for less than 100$ 5x5 with 1 or 8x8 with 2 lights. Buy ac and venting fans to cool the room. Run the room for acouple days while checking humidity temps and light leaks. When that is accomplished you need to find a strain and IMO use soil or coco your first time so you can spend your time learning nutrients,deficiency and training for your strain and how much time your able to spend in the room. You start right into hydro you will spend more time keeping your system clean and maintained and nutrient issues then be able to learn to read the plant and train the plant. People get 2 lb off 1 light all the time. Its because they will take each plant and care for it and train it. Starting with a big setup and mult. Rooms there is no chance you can train and go through every single plant with detail. Idc if you spen 10hours in your room, without the experience you will oversee a ton of stuff.
As for alittle advice i learned from my experience is that a healthy plant does not mean it is living up to its potential. I rand a basic hydro ebb n flow for a good while. My plants always stood tall and grew awesome(so i though). They grew 3x faster than soil and just way better altogether. Still my yeild and plant size vs my veg time were just shit compared to these other guys i knew. After spending more money on my setup(fairly large size from the start) i began seeing even more amazing growth. The root structure is EVERYTHING. Keep enviroment in tact is easy once the money is spent right.but with nutrients and water moving and worrying about algae is a big deal. Plants love food/oxygen in the root zone. Too much of each will hurt it. Either dry out of burn them. If you do hydro pay attention to this because you will have healthy plants but slow growth and not even notice the potential your missing. Find a setup you know and are capable of using to provide the most water and oxygen as often as possible. If soil then learn about micro organisms and amending your soil properly. My experience, i will never use a ebb n flow again because the growth sucks compared to a bubble bucket or undercurrent. The plant getting fed for 15 min several times kept them healthy but not at thier potential...
I know this seems like all obvious things and will be dismissed but a year from now you will have changed your setup multiple times and spent a ton because you started big without seeing what you capable of... why have 24 plant pull 6 lbs off 6 lights when you could have 12 plants pull 6 lbs for 4 lights. After afew grows youll understand where im coming from alittle more im sure.
Id say learn to get atleast 6oz a plant before doing 3 or more lights. If your not getting that off less than 4 week veg then no point in spending big money on big setup. Whether it is enviromental issue/ light issue/food or training. They all take time to learn.