Here is only the information why should get these items not in which order you should buy them, if you want to see the purchase order go to the top and watch under "Purchase Order"!!!

AD Carry

You want to buy these boots because it gives the most amout of movement speed in battles and that means more attack damage because of Hecarim's passive ( Warpath), and the extra movement speed is always nice to have.

This item is a must have on Hecarim because his Q ( Rampage) has a very low cooldown and you are spamming it in fights so you activates your sheen that increases your next attack with 150% damage.

The Bloodthirster is also a must have when playing Hecarim as a AD carry because of the high damage and lifesteal that it gives. As you can see at the top under "Purchase Order" I'm buying two Bloodthirster, the first one before phantom dancers and the second one after.

Phantom Dancer is a standard item for AD carrys, it gives good amount of attack speed and critical strike chance and also movement speed, and movement speed means attack damage for Hecarim.

This is the last item I'm buying and I'm getting this because of the high damage and critical strike chance but most because it increases the critical strike damage to 250% instead of 200%, and that is great. Usually at the end when I got all my items I crit 1350 on minions and around 900-1100 on champions.

My standard build looks like this:


But you need to adapt to your enemys, I'm giving examples how you can change the build to adapt to your enemys.

Good Against HP Tanks:


Good Against Armor Tanks:
or

Good Against High AP Team:


Good Against High AD team:
or