Here is the list on quests i can help with. Note: Before i can help you you have too do all quests on north island since those quests lock up quests later in game and you might need your own transport for quest like getting magellan.

South Island: can do all if you have transport for some quests and that you are lvl 20+. Note: for magellan quest you need a steam ship or a plane too get too his ship that is near south island and for La. Tim quest you need only a plane but might need too go back and forth too pick up more for team XD.

Oslya: can do some quests but not sure about elin gun or getting arez.

China: can do all quests there too depending what lvl and element you are.

Japan (Kyoto): can help with kanako and some more quests but haven`t done many quests there yet so i`m not sure.

Mayan: can help with shasha quest but not many other quests there.

Well that`s the quests i can help with for now since i have been only too those places. Hope this is helpful too you all.