How do I hook up the motors to the wheels?

[pilleya]

If this is for a non-FRC project, then you don't need to adhere to typical allowed motors.

Cost is obviously important for you, I would suggest looking at the gearboxes and motors sold by BaneBots, their gearboxes and motors are on sale at the moment, same with their wheels.

http://www.banebots.com/category/P60_7.html

The motors you select are dependent on the weight and size of your robot.

But a 550 or 775 motor should easily be fine, for a driving a decently sized robot

http://www.banebots.com/product/M5-RS550-12.html

http://www.banebots.com/product/M7-RS775-18.html

For wheels have a look at these http://www.banebots.com/category/COLSON_WHEELS.html and these

http://www.banebots.com/category/COLSON_HUBS.html

With a robots project, the motor controllers are going to be a big cost component and would probably be about $45 if you went for the low cost REV Spark