Is the whole thing something like 800 km?
There are many ways and you only do what you want. You can start in Prague for what it's worth, as long as you walk, ride a bike or a horse to Santiago, you're doing it right.
For you to get the Compostela (the certificate in Latin) you need to either walk more than 100kms or ride yourbike/horse for more than 200, and obviously have your Credentials stamped, because that is the proof that you were indeed a Pilgrim.
People come from all over the world really and they take different roads.