Choose Human or Elf
The race that you select will impact:
Look and feel of the buildings
Size and orientation of the buildings
The types of army units you'll be able to use in battle
While there are advantages and disadvantages for each race, neither is necessarily better than the other for faster progression through the game.
All things considered, the races are equal in this regard.
The race you find 'easiest' or 'fastest' for game progression may likely come down to your play style and frequency.
Next, you'll decide if you want to be human or elf.
Once this is set, it cannot be changed. Choose carefully!
For the most part, this just comes down to preference of what buildings you like more, and which is more interesting to you.
There are some differences between the races however that you may find helpful to know.