What do you do after you beat the third gym leader in pokemon saphire?

Question

Do you have to cross the desert in route 111 ? do you go to another city or town ?

Answer 1

You have two choices. Either go to the West and win a contest plus get an HM and a shortcut to Rustburo or go North. You must go to the West of the desert, because you can't go through the desert yet. Try to find a cave, go through the cave (you can tell you are there because of the steam pockets.) continue on from ther, it is pretty straight foward.