Buildings
In the beginning you should focus on resources. Just click the village overview and choose one field out of the 18 resourcefields (lumber, clay, iron and crop).
Later in the game you'll have to option to build more advanced buildings which will be listed when you click an empty spot in your village.
Village overview
The basis of your village are resources, you need them for simply everything, in Travian there are Lumber, Clay, Iron and Crop.
The resource are being produced at the village overview resp. the resourcetiles there of which each village has 18. The first village has always 4 Woodcutters, 4 Clay pits, 4 Iron mines and 6 Croplands but other lands around your village may have other distributions. It is always best to get a second village with 15 Croplands. if this is unachievable as they are quite rare get a village with 10 croplands and then an annex oases that produces 25% extra crop.
In the beginning the resource tiles are not extended (level 0 out of 10 for normal villages). Level 0 resourcetiles only produce 2 of the resource per hour. When you have enough resources in your warehouse you can extend your fields, by clicking on them. Something like this will appear:
Village center
In the village center you see a number of building sites. Each can only be occupied by one building at a a time. Normally you can use any building site for any building but there are two exceptions, the rally point and the wall.
Furthermore every building except the cranny, the warehouse and the granary can only be built one time per village. Of the other three you can build as many as you like per village after you build at least one of the type to the maximum level.(Cranny level 10, warehouse and granary level 20)
The buildings have different uses which are of political, economic or militaric nature. In addition you have to fulfil certain prerequisites for each building before you can build them.
Be careful with the red X, you won't get the costs fully refounded after canceling a construction order!