if you are on Agnarr then you can get a few in Friona Vie or Overthere and mob drops.. For Velious spells most are mob drop except the travel spells which can be bought in freeport / plane of growth. If you are not a porting class, then i think each class gets a couple vendor bought spells and you can buy them in skyshrine or thurgadin
If its live server I recommend using your find button and looking for cleric spells level 50-whatever then follow the yellow path. You can use this for other levels and classes. If your on TLP then I recommend using the TLP forums.