I haven't read all the comments so excuse me if I repeat anything.

Saying "Such and such drops in this turn so don't get that" is pretty stupid. RNG is a bitch. I've done coil a ridiculous amount of times and I haven't seen a shield, boots or legs drop. But I know other people that have got it all. It's just luck.

I would upgrade your sword first. Some people are against it but it's the best thing till Allagan and you probably won't get that for quite a while. When you're on turn 4 and you've got DPS burning everything like mad (especially soldiers and knights) you'll be glad you upgraded that sword.

I've got full myth with belt of light (waiting for Allagan) and Allagan accs (+hero ring) with DL earring and Bracelet. Just away to upgrade my bracelet but holding out for Allagan earrings because holding for 2 pieces isn't gonna nerf me.

The first myth I upgraded was Body since it's BiS. Problem is you have to settle for Hoplite circlet or try for CT helm. I then went for my myth circlet to fill the gap (Allagan helm drops in T4 which is BiS but RNG is a bitch). Basically go for things to fill voids. Myth gloves are always a winner.

I went full Myth because my luck in coil sucks. You might get all the drops so just get what you need. Not what people tell you.