Aegis' Custom Build

 1st item:

Bloody Key (if I'm going for 200+ kills Golden Key)

2nd item:

If my hero can't attack air otherwise progress to 3rd item instantly
Orb
* If Tank, Orb of Slow (for the slow, especially good for Owl-Quest, and against heroes once maxed)
* If Melee Bruiser, Orb of Corruption (for the armor reduction)
* If Caster-Tank who has good AoE, Orb of Flame (for the Splash)

3rd item:

Boots of Exp (First item I level up to lvl 3 instead of going goldmine so I reach lvl 30+ for ending)

4th item:

Silver Slaughter/Blood Soaker if I'm squishy/Firefly Egg of Corruption if I'm support

5th item:

Medallion of Strength/Helm of Valor/Flag of Courage (Medallion/Flag is usually the 2nd item I up to max or just lvl 2 if I also need to up my Mana Stone)

6th item:

Skull of Eternity/Mana Stone/Frostmourne (Mana Stone lvl 2 is usually enough to leech the mana of endgame bosses)

In addition getting the Urn of King Terenas will give you Spirit of Kel'thuzad which gives +1 point for each hero killed which is essential for late-game build.