The market is usually one of the last normal buildings obtained, due to the sheer silver cost of the cave.
Btw, when leveling villages, each level increases resources gained every 5 minutes by the world speed. In Alpha/Beta this would be 2, in Gamma this would be 3, and in a speed 1 world, it would obviously be 1.
As for building/tech requirements, they can be found simply by moving your mouse over the building or tech in the senate or academy respectively. With one exception (barracks requires lvl 1 silver mine), all buildings require the buildings above them to be at least certain level to build and/or upgrade. Techs just require a certain academy level (every 3 levels leads to a new set) and an amount of research points (4 per academy level). Oh, and everything requires resources, though that should be obvious.
Troops and ships just require their techs and respective building, excluding horsemen (lvl 10 barracks), chariots (lvl 15 barracks), colony ship (lvl 20 harbor), and myth units (various temple lvls).
There is no level where you silver mine "should" be. It probably shouldn't be overly high sure, but there is no specific level, or even level gap where it should be. If you need more silver, level it up. Simple as that.