The Earth's magnetic field is far too weak to provide much force to a spacecraft. At LEO the earth's magnetic field is probably somewhere around 50 microteslas, or 50,000 nanoteslas (it varies greatly by your position above the Earth) in intensity.
The Earth's field ranges between approximately 25,000 and 65,000 nT
(0.25–0.65 G). By comparison, a strong refrigerator magnet has a field
of about 10,000,000 nanoteslas (100 G).
So a refrigerator magnet is 200 times more powerful than the Earth's magnetic field. In order to convert this force to movement you'd need to interact with the earth's magnetic field with an incredibly powerful magnet field which your spacecraft would have to generate. This would be 1) very heavy and 2) the magnetic field would be hazardous to people and equipment on board. Even with a massively powerful magnetic field on a spacecraft you would not get much propulsion out of it due to the earth's weak field.
Lastly, magnetic fields quickly reduce in strength the farther away you get from the source, meaning you would need another form or propulsion for course corrections.