Returning mage from TBC. Basic help

[Varrusian]

Hello there! This is my first time on this website. and this is my first time playing a Mage since The Burning Crusade. so it's been a while. so i am just looking for some basic information that is up to date. I should preface this by saying i currently play a Shadow Priest in my guild that is progressing through Mythic HFC. i wish to get this Mage to a point at which i can use him to progress through mythic as well. This Mage is also a candidate for my main in Legion as well.

My first question is; As a Mage that is starting out what specs should i be playing while getting into normal HFC

Second, I see a lot of Mages going both Fire and Arcane. So at which point should/do i drop Frost for the before mentioned specs. Is going Fire/Arcane tier dependant?

Third, How important is 4 piece? is it mandatory to obtain?

Thank you for taking the time to read my post, and helping this noob return to his roots.

[Curnivore]

Fire is mainly a gimmick spec used by overgeared people already in guilds on 13/13 that kill bosses in a couple of minutes usually. Or that's the current trend at least of the last month that showed an increased number of them, there is still a minority that still plays it no matter what. It's very hectic if the strategy doesn't allow a perfect alignment of the the automatically-procing trinket it needs and its utility is not much more than mass AOE.

Arcane is very reliable on single target and almost always the best spec there but it's hectic on mass AOE since most of the top parses are relying on random procs of a trinket.

Frost is extremely reliable on what it does since it will never fluctuate too much between pulls and it can slow down dpsing reliably, but it will never be too impressive.

[Zelendria]

I'd play the spec you prefer the most TBH. Frost tends to have the edge on Arcane at lower gear levels, and also when you don't have tier and trinkets. However, if you don't like it I doubt it matters much at this point in the tier.

Fire needs a lot of gear and you need to buy a Sandmans Pouch or craft one if you can.

I wouldn't say anything in this game outside of top guilds is mandatory. However, it really is in your best interest to pick up tier, class trinket, PoF and legendary ring. All of these add up to a huge boost in DPS. You would probably double your DPS overnight going from random bits of gear to all of it in one go.

[Varrusian]

So i should go Arcane on most fights when i have tier and PoF and maybe class trinket?