it doesn’t matter what level your character or items are. the only two things that really matter are, do you really want it on your Build and does it fit with what your Build does.
right now, I have all level 1 Equipment for my Rogue & Warrior Ascending Builds. when I first made them, they all had a Mythic Affix and all other spaces were Myth Stones (except for the Pet, no Myth Stones or Mythic Affixes can go on them).
Ways to reveal Mythic Affix Recipe’s:
you can experiment by putting 4 random Myth Stones on an Item with 4 Sockets, and hope it makes a Mythic.
every time you place or remove a Myth Stone from an Item, there is a chance to reveal one random ? of a Mythic Recipe. each Mythic has 4 question marks (?) hiding part of a Recipe.
converting a Myth Stone to the next lower Myth Stone, or 2 Myth Stones to the next higher Myth Stone has a chance to reveal part of a Recipe.
the higher the Tier (Normal, Rare, Ultra Rare) of the Myth Stone used or converted, the better chance for a part of a Recipe to be revealed.
Hope a Player will share a Recipe.
if you can’t wait for any of the above 
, here is a Post with all of the Recipe’s 
.
it doesn’t matter which order you put the Myth Stones onto an Item to make a Mythic Affix. it only matters that you have the correct Myth Stones.