A 9 × 9 house you can build on your first day. It takes only 361 blocks, and 323 of them are oak planks and dark oak planks — chop some trees and you have nearly everything. 9 layers tall.
It is the most basic house shape: plank floor, log posts at the four corners, two windows per wall and a stepped roof. It is also a good size for learning to read a layer pattern.
Layer by layer
LAYER 1 — floor. Fill 9 × 9 with 81 oak planks.
LAYER 2 — first wall row and furniture. Oak logs at the four corners, planks around the rest. Place 3 bookshelves, 2 furnaces, a wool bed, a crafting table and a flower pot inside before closing the walls. Leave the door gap open.
LAYER 3 — windows. Two glass per wall, eight in total, so you can see out in all four directions.
LAYER 4–5 — upper walls and lights. Set four glowstone into LAYER 5. No glowstone yet? Torches on the walls work too.
LAYER 6–9 — roof. Cover 9 × 9 with dark oak planks, then step in to 7 × 7, 3 × 3 and a single block. There are no stairs, so there is no facing to get wrong.
Materials — how many trees?
183 oak planks come from 46 logs (1 log → 4 planks) and 140 dark oak planks from 35 dark oak logs. Add the 16 oak logs for the posts and it is 62 oak logs and 35 dark oak logs. Dark oak only grows in dark forests; if there is none nearby, use oak or spruce planks for the roof.
Smelt 8 sand for the glass. Bookshelves need books, so fill them in later; the white wool bed takes two sheep.
Tips
Put the door in the empty wall cell on the pattern. On Hard difficulty zombies can break wooden doors, so consider an iron door or a fence gate.
Finish the lights before the roof goes on. A dark interior spawns mobs just like the outside.
To make it bigger, build two copies side by side and open the shared wall instead of stretching the walls — the roof keeps its shape that way.