With the Dorans items it's easy at the beginning for killing creeps.
As a AD Character it's very important to kill creep with "Siphoning Strike".
If you have "Spirit Fire" and a Range Laning Partner it's easy to do some Dmg.
If you wanna kill the enemey on the lane focus 1 with "Wither" and "Spirit Fire" , are you in Range with Exhaust you have a massive slow and can kill the focused easy.
Nasus is a Minions destroyer : "Siphoning Strike and "Spirit Fire" are Perfect to do this.
So kill creep and support with "Spirit Fire" and "Wither".

You start with 100HP + 10Armor + Life Reg, it's perfect to jungle.
You can get a pull by the golems and go, by 550 life use smite for 1. , 1 melee and then "Siphoning Strike" , the 2. will go easy then.
Now you're Lvl 2 and have to skill "Spirit Fire" for the Ghostes, try to kill at least 2 of them with "Siphoning Strike". The Wolves are to healing with your life steal.
For blue ask mid for pull with a long range attack, beginn with "Spirit Fire" , after "Siphoning Strike" and 2-3 melee attacks use smite kill him with these attack too.
Now you're ready to gank with "Wither".