My most used set by far is the Barbarian Armour. I have it upgraded to lvl 2, except for the headwear because I don't remember why. I love the way it looks and the attack bonus is very welcome. I usually put on the climbers bandanna if I have a lot of climbing to do, but I rarely/never wear the full climbing set because I don't really like the way it looks as a whole.
Although I got the Korok Mask recently so I've been wearing that a fair bit too to help with my 100% goal. And I use the Champion's Tunic occasionally, but not often; usually just when fighting difficult enemies so I can see how much HP they have.