Welcome to AFN newb, stop by the Intro's section when you have a moment and give a shout out.
If you look at the stickys in the thread you are posting in there are several answers to your questions. Beginners guide to dirt as well as many others. There is no hard and fast rule with growing, just go slow with the nutes on Autos.
There is also an awesome search bar in the upper right hand corner that says "Live Search", give it a try and you will be amazed at how much info is at your fingertips.