This is an build I have been testing and seems to do well.

The main variation on a standard AD build is the inclusion of Guinso's Rageblade. With 0 stacks, this item boosts Blighted Quiver to 18% (6*3) and stacked boosts it too 21% (7*3). This allows you to blow up tanky opponents almost as quickly as squishy ones.

We will be leveling Blighted Quiver first to give us the better chance of getting some kills in lane. This also helps a lot with minion farm and I rarely have mana issues with this build.

You can get Hail of Arrows or Piercing Arrow first, you will be using it to proc your Blighted Quiver stacks. I prefer Hail of Arrows for the slow.

You need to trigger your blighted arrows as soon as you get 2-3 stacked on them. strive for 3, but you can go for less if you think the debuff will expire.

Get a Doran's Blade or Boots first, depending on your lane. If you have a good support, you can go with a DB.

I get Berserker's Greaves soon so I can escape better. Varus has horrible base speed.

Guinso's Rageblade you can buy at a time when they are starting to get beefier. It will help blast away their health. Giving you 6-7% of their health per stack.

If you feel you are having issues with casters nuking you, you need to get a Banshee's Veil. Another viable survivability Item is Guardian Angel.

I always get flash because it can help you either get to a safe position or move close enough for the kill.

For the other skill you can get whatever you want. Heal, Exhaust, and Ignite are all viable options. I prefer Heal because I am usually out of range for the other two when I need them. Exhaust can be excellent to keep melee AD's off of you. Ignite is always useful for shutting down an opponent's health gain. Ignite + Hail of Arrows is quite potent.