You just brewed this last weekend? Make sure this is done fermenting before dry hopping. I suggest waiting another week. If your yeast is still active, it will bond with your hop oils and drop them out of the beer.
Since you're newer to brewing and are still figuring out the hops and their flavors, you have an opportunity to try something here that is simple but will give you two pleasant results. Try dry hopping five gallons with 3 oz of cascade. Like said above, you'll have a great flavor and aroma of cascade working together. With the other 5 gallons, try using 2-3 oz of chinook. You'll get a more piney aroma from chinook and it will work well with your late addition cascades.
Note: This many dry hops will make this more IPAish if that's what you're looking for. If not, cut the additions down a bit. I use at least 5 oz dry hops per 5 gal in my IPAs, but I suggest starting with 2 or 3 oz and go up from there for your likings for an IPA.