do you know what kind of nutes you are going to use? one key thing to remember about the autoflowering plants is that it flowers no matter what the light cycle is. i've only grown 2 auto plants once and i used a 20/4 under a 400w hps and the buds were dense and was ultimately satisfied with the results.
as with any grow, lights, nutes, and ventilation are the most important aspects of each grow that determine the quality of the end product. since this is your first grow, i cannot stress how important ventilation is. not only does air circulation across the plants increase the strength of the stalk, but it also minimizes the chance of mold which can destroy all your product. gradually increase the concentration of your nutes over time and be sure not to give too much or you'll burn your plant. good luck with your first grow and keep us tuned in on your progress!