while you harrasing your opponent and collecting money, build up some gold to buy aghanim, so that your laguna can hit total damage 1250. not enough just that yet, and buy refresher orb so your laguna which has total damage 1250 can be used twice. it does hurt. to cover up the mana usage for double laguna attack, buy bloodstone for mana regen and total mana.
if u want your double laguna do more attack, buy and use ethereal blade so your twice 1250 + 40% again, it's a sure kill. still not enough? buy dagon. so after using laguna, use dagon and then refresher then laguna and dagon again. sure kill.
your job here is for killing opponent. much of them. if one of your friend died and leave the lane not defended, go there defend there. make sure your opponent run if they see you. if they run, not to worry, try to stun them and kill them with double laguna attack.