Fresh 80 dungeon spec.

Hello. I've got fresh 80 lvl mage, around 3k GS right now. I've read guides and from them i get info that i should be Arcane for PvE, and around T10 i should switch to Fire. My question is, considering 5-5.3K GS is obtainable with vote shop and rhc, should i really be Arcane even when 90% of the dungeon is trash AoE fights? I know Arcane is inferior in terms of AoE, and I wont be raiding before 5k GS for sure. And If I should stay Arcane anyway, is there a more optimized way to do AoE DMG than just spam blizzard? Ty for answers!

Half of weekly raid quests are doable for 4k gs, you can go ToC10 as 4.6+ (depends from how lazy is RL) and so on. And any mage spec can AoE properly (flame strike + blizzard), it's better to be good in solo dmg than AoE.
Ofc there is this funny mage spec with blast wave + dragon breathe)