@Wack i always add mythic first.
- crystal affix
- legendary affix
- epic affix
For example why mythic first:
If you have an weapon for example:
1x set affix, 2x leg affix 3x epic affix.
To add now crystal affix you have to remove 1 epic affix -> item has now 1x set 1x crystall 2x leg 2x epic. If i now want to add mythic i have to remove all stats. -> 1x set 1x crystal 4x socket
On a weapon i want %weapon dmg or %element damage but i must remove it if i add crystal first and cant roll it again with ruby.