One 11-12 gram pack of dry yeast is just about perfect for 5 gallons of a 1.050 beer, like an APA might be. The
Mr.Malty Yeast Calculator is a great resource for determining how much yeast you should use for a particular beer and it includes dry yeast.
You should avoid making a starter with dry yeast, because it is made with healthy stores of nutrients that are difficult to equal with a starter. Rehydrating the yeast, however, if done correctly, can lead to healthier yeast and faster fermentation.
You can sprinkle dry or rehydrate, but be aware that sprinkling directly into the wort can halve the viability of the yeast.