Wheels are the biggest upgrade bang for the buck. Light wheels are a revelation. A 1,400 gram wheelset is joy. A 1,000 gram wheelset (carbon tubulars) is a religious experience.

My riding profile seems not too different from yours. I have a garage full of wheels, so here is my advice in no particular order:

• Go light over aero. I have racks of expensive deep profile alu and carbon rims that collect cobwebs. Unless I'm riding long miles on the flats, the light wheels are preferred.
• Go alu for general riding. If you can afford another set of wheels later on, lightweight carbon would be next.
• Carbon clinchers: no.
• If you have a 10-speed drivetrain, then get a Shimano wheel with a 10-speed freehub. 11-speed wheels are inferior in terms of dish and spoke tension differentials. Plus 10-speed wheels are being blown out by vendors and ex-racers. Much cheaper and superior structural integrity.
• Ultegra 6800: like tubeless-compatible wheels in general, field repairs are impossible. Unless you carry big metal tire levers and a couple of spare tires for when you destroy the tire beads on the tires you're trying to remove.
• Shimano rear hubs are by far the best - in terms of the (loose ball) implementation, the freehub design, and the resistance to water and dirt ingress. Plus the ability to source replacement parts. Stay away from overrated and overpriced boutique hubs.
• The better Campagnolo and Fulcrum wheels are pretty good- the G3 and 2:1 rear spoke patterns on the rear wheels make a lot of sense. I am riding Eurus wheels right now - very stable, light (for clinchers), and reasonably aero.