UV sanitizers, Ionizers and ozonators are all supplemental pieces of equipment that can help you but will not sanitize your pool on their own. I would suggest putting off the purchase of any of these units until you are familiar with operating your pool with chlorine alone.
Salt water chlorine generators and chlorinators both add chlorine to the water, which will probably be your sanitizer of choice (bromine and biguanide products are recognized and available, but I would highly advise against either for an outdoor pool).
The salt water systems are by far the best solution, in my opinion. They don't add calcium or stabilizer to the water, they don't require you to store buckets of chlorine, and they deliver a constant (and variable) amount of chlorine into the water.