Take the starter off and put power direct onto it via some jump leads - does it spin ? If not bin it.

You will need +ive on the big terminal and a -ive via the casing (not via any terminals). If it spins the motor is fine. Then bridge the +ive across to the smaller terminal for the solonoid and see if thats working.

The lead from your alternater should be a +ive btw.

If the starter spins off the car then there is a wiring fault from the ign switch to starter, an earthing fault to engine or the batterys flat lol Hope that offers some help