The Haladin crossed the Blue Mountains 318 years after Mortals were awakened at Hildorien, give or take 2 years. This project uses the flat world chronology in which Men awakened with the first Sunrise, and the Annals of Aman, Grey Annals, and later Tale of Years gives us dates for the events of the First Age.
I would prefer to base Elves' clothes and armor on cultures living in temperate climates, because that's where Elves live. Maybe warm temperate climates, since they're more cold-hardy than Mortals and so they dress in fewer warm layers.
Leather armor is indeed a D&D trope, but it is also the only flexible armor available to people who haven't yet learned to weave (or trade for) cloth. I do imagine the Edain could have cloth when they first come to Beleriand.. but it's possible they don't yet. In the real world, people apparently didn't use more than regular clothes for armor until the Bronze Age, but they also weren't up against the armies of the Devil. So... Fire and clothing they would certainly have. The Hadorians even had herds of livestock. And I imagine they all had dogs.
Anyway, keep in mind that we didn't show Orcs existing at all until Morgoth returned to Angband, so there was nothing for Men in the East to have to fight except for large evil animals/monsters, and each other.