I just finished my first grow and here are the most important things for growing...
1) GET A 400WATT HPS light or higher! This is the most important factor.
2) Make sure your room stays between 65-85 and that you have some air coming into the room, but lots of outtake, it really helps with heat.
3) Get a basic nutrition system, a good grow solution and good bloom solution, all the extras you wont need and start off using half the recommend dose.
4) DONT OVER WATER if in soil, water them fully once, then wait until the bucket is dry and light, you can test it by picking it up. Roots grow by searching for water, so let them search till there is none left, then fully water again.
I wish I had of known these things on my first grow.