Starting a Fire team from scratch, huh... hmm.

Well, Amaterasu is a must, yes. In February, Mars is a must.
Aside from that, I think you're fairly free in what to bring in Fire? Svarog is good sure, and gains an awakening around late January. Ares gains awakening late March. I guess that's all four.

But if you're looking into other elements with the intention of getting all the Miracle tickets, I think Darkness and Water stand above the rest. Darkness has Amon with -25% Def A frame, though I guess with the upcoming -50% debuff cap at Valentine event kinda makes that moot. Osiris is a great healer, coming out late October. Darkness Amaterasu... is sadly limited, so you can't get her with Miracle tickets. Darkness is also the first to get the +45% Elemental Eidolon, from Halloween event. And keep in mind that there's no bad match-ups for Darkness at all.

For Water, well, pick any SSRs. They're all so incredibly broken it is unbelieveable. Well, I guess Shiva is on standard powerlevels. Poseidon? Atk -20% A, debuff prevention. Aphrodite? Heals, cleanse. Ryu-Oh? Atk -20% A, Def -20% A, Overdrive extension. SSR Nike, heals, Atk -15% A. Cthulhu, freaking C frame -20% and Overdrive reduction. So I guess pick Ryu-Oh and Cthulhu and you're good to go, bring Sniper Shot for extremely good debuffs. In December we're prooooobably getting Water Raphael who has -15% B, so you're hitting -35% Atk -55% Def and even Black Propaganda, all without using your Soul yet.

The encyclopedia in Sanahtlig's toolbox gives you a quick peek on all the upcoming SSRs if you want to quickly see stuff like this for yourself.