This is the build I use almost every game for Darius. It combines good survivability with amazing damage output. There are some things I would swap out in certain instances but that will be talked about during their respective sections.

I go with Flat AD Marks, Seals and Quints for good a good early game and some added damage late/end game. MR Blues help at any stage of the game and could be swapped for MR Per Lvl's and work just fine. If you know what your are up against you could even switch the Yellow's for Armour Seals and do well.

I pick up Cloth Armour first because I do not have any armour runes and having some early sustain is never bad. After getting my boots I'll finish the cloth armour into a Wriggle's Lantern. I grab Attack Speed boots because they increase Darius' damage quite nicely but if needed I'll go with Tabi or Merc Treads. Aside from the Bloodthirster, everything else is a must for me, I'll switch the BT our for a Maw if I need more MR end game.

Slightly tanky build with awesome damage and capable of killing almost any champion early or end game. Thanks for reading my first build :D