If your going for yield, I wouldn't go auto. There is no control for size when it starts to flower. Every auto I have grown starts to bud when its a foot tall or less and the best I have harvested was 1 ounce.
with my hydro grow for photo period, it takes 4-6 weeks in veg, I wait till they are as close to 20 inches as possible. Sometimes over and sometimes under. Then the flower time depends on plant. The yield depends mostly on wattage. A good goal to shoot for is .5 per watt. Some say 1g per watt, and sure thats a great goal, but I have a decent set up, and I've been doing it almost 2 years now and I haven't hit that yet. Genetics matter, as does grow style and nutrients, but the best ball park estimate is to compare your wattage used on the plants.
So what kinda lights are you using? How do you plan on growing? WHAT are you planning on growing?
From seed is a bit slower but its the cleaner option. No worries about over cloned clones, bugs, or disease. I started with clones and after about 6 months started a new room with seeds to illiminate problems. It worked but for a first timmer I would suggest getting a clone, it just skips a step you can learn down the road.
Anyway, I digress.
I suggest photoperiod. It takes me about 12-13 weeks total, from cloning to chopping down, and I get on average 3-4 ounces a plant. My highest has been 6, and once in a while I get a few 2 ouncers.
With auto I get 1/2 ounce average. For about 8 weeks.
So by my math thats 4 ounces for 90 days or so. Or 1/2 ounce for 60. I'd go photo period. Plus you can clone them and keep going. Gotta seed yourself or buy new seeds every auto flower run.