depends what gear you have already and class

For tank

Scenario 1 - DL only and relic weapon

- I would suggest saving for the relic body first as this will give you the most vit return for your myth
- Next I would then go for the head piece
- now you should have a decent amount of HP to do most endgame and a few coil levels
- Next you have a choice to upgrade shield or wait and upgrade pants
- after upgrade gauntlets and or boots.
- finally I would upgrade the one lvl 60 ring you have.
- last I would start replacing DL accessories.

Scenario 2

Run coil 1 a few times see what drops you get and upgrade according to best investment.

All in all it depends on 2 main factors

1. how often do you run coil 1 or 2 and win.
2. how many myth tomes have you got and how long you are willing to wait.