When you chose foucs,you can go with teamates to kill or solo to kill all marine.Becareful!,if yuo want solo,you want have very good control.
Level 3:The last to upgrade skulk(must upgraded skill).you can chose Celerity or SoF.if you have clocking, i think SoF is best,it can know all the marine where,and hide to road,wait the marine come to die.He is can't see you and you can know and see him(very good killer machine haha),but the marine have scan you want to go back!Because you didn'y have focus and Celerity so yuo will die on marine's shot.
Or you can use Celerity and focus(you are the super killer now=.=\/)But the problem is you want have very very very good control).
Level 4:Here,you can chose go to fade or still do skulk,when you can chose fade,you only can wait three points.I usually use this.or you like skulk (Ya,I like very much Because it is very fast and have good damage[have focus you have one hit to marine and have 140 damage to him!])
Levle 5-10: level 5 to level 10, you can chose all upgrade or go to onos.(i always upgrade focus,celerity,SoF,xxxx[i don't know how to spell,it will +your amnor] and then go to fade,start to kill all marine ,they all my food now haha
I hope this topic can help some players to do the alies, thanks you^o^
And the last thing is My name in the ns game is [james]Don't forget it!And do not use my lovely name =.=\/