The most cost effective way is to get some thick rubble sacks and pull the whole lot off!!!!!
If the tiles are going to ruin the first few bits of plasterboard get back to the stud work and replace all the boards. That way you will be able to retile straight to the plasterboard 32kg of weight /sq metre and save time and money trying to patch up holes.
Normally I just use a bolster, sometimes an old large chisel. You just have to feel around for the best place to attack each tile. If the plasterboard is coming off, just go with it and take the whole lot off. It's no big deal. Plasterboard is cheap, or you may want to put up backer board instead.