I would definitely recommend starting smaller if you have no background to any kind of art, but if you're already adept in other forms of art (e.g. digital, traditional, painting etc.), you could definitely have an easier time in making bigger pieces.
As for the piece itself, it's actually pretty nice! The level of detail is not really the most important part of pixel art, I would definitely put readability above it. Cramming in too much detail can make a piece very noisy, and it hurts the readability. I would definitely recommend working on your cluster-work and colours. Learn hue-shifting, brightness and saturation.