If you like a sweet rub, then you would obviously start with a sugar base... brown sugar being most common. After that I would at least do salt and cayane pepper. That would give you a sweet savory flavor with just a little kick at the end from the cayane (depending on how heavy you go on the cayane).
If you do that be real carfull not to let your temps get to high... sugar burns fast and then tastes yucky! I use a brown sugar base on my rub and add all the usual suspects - garlic, onion, cinnamon, paprika, ect. plus whatever else strikes my fancy. One great suggestion is to buy whole fennel and whole cummin seeds, dry roast them in a pan on the stove, then grind them in an old coffee grinder. That is a wonderfull flavor with pork!
Start small and build your layers of flavor, only make one or two changes from smoke to smoke so you can keep track of what does and doesn't work. Best of luck and don't be afraid to experement.