Definitely get a scale as Tony mentioned.
The amount of smoke is very subjective and you will find many different opinions here. The best thing to do is try some different amounts until you find what is right for you. But, here are some rough guidelines for how much wood to use (all in ounces):
Ribs - 2-3
Chicken - 2
Turkey - 2-3
Brisket - 5-6
Pork Butt - 5-6
Fish - 2
I rarely open my smoker during a smoke and it is so airtight and keeps moisture in that I don't really think the spritzer is really necessary unless you want to use it impart some flavor on the meat once you pull it out. But the Smokin-It smokers are unless stick burners and other less than air tight smokers that need additional moisture applied.
One thing I would get is a bunch of tin mini-loaf pans as this is really the best way to add extra moisture to your smokes. Fill one of them with Apple Juice/Cider, Beer, or even water and set the pan right up against the smoker box. I pretty must use a water pan for all of my smokes except for fish, poultry, jerky, and snack stix.
If you plan to do any jerky or snack stix, I would recommend getting a James Jerky Dryer as the airtightness of these smokers is a detriment when you are purposely trying to dry out a meat like a jerky or a snack stick.
These are the main things. Once you get going, you may wan to add an Auber Control Unit. But this is not necessary to have great smokes. It just gives you a bit more versatility.
Well, I don't want to bombard you with too much stuff, but this should get you started. We'll see what others have to contribute as well.