First the toe, then the foot, and before you know it you’ll be a Flashaholic like us. You will be happy, but your bank account may not be. So be happy, you’ll earn more money later 
First learn about safety HERE then decide where to expand. You’ve got a good charger and some decent cells but you’re going to want to go into 18650/26650 lights. You’re going to want a ‘mini’, a thrower, an EDC, and a flooder or lantern. Plus maybe a headlight. So many toys, so little time, so make the best of it and start with whichever kind of light it is that you don’t have but could use. Go with what’s highly and widely recommended here on BLF and you can’t go wrong- those lights are where the best value is found. “Special Edition” and GB lights can be great if they’re what you’re looking for, but sometimes they are specialized for one purpose which may not be your “cup of tea”. Before long you’ll know exactly what you want and who has it for the cheapest. And if you’re so inclined modding can give you more for less or even things unavailable otherwise.
Lots of fascinating things to learn about here- it’s a lot more than a battery, bulb, and reflector nowadays so enjoy and be happy!
Phil