I thought the elements were pretty much spot on... Your main element (especially your first team) is pretty much going to be determined by your draw...

In my case, my draws are all over the place initially... I had Poseidon and Michael from the first 6k, and the SSR guaranteed pack gave me Acala... After a while RNG says here's Amaterasu, here's Brynhildr and I knew I just had to go fire...

It will be hard to tell which element you need to focus early on, because it will be determined by how lucky you are. If you're in the mid-game or late game, then you should have enough game mechanic knowledge to know what element you want to work on, and start saving your crystals and tickets (maybe $$$) for double rate gacha for the element you desire.

As for 3rd tier soul, I'm relatively new to the game, but I'd think Andromeda is the safest option for beginners. I find using non-Andromeda 3rd tier soul work best when you have the necessary hime to make the team works. I see souls as a complementary pieces to your team, not the core of the team...