Many helpful tips:
1)When you are almost out of mana, but you know that you will need it at later, deactivate ricochet and gain some mana.
2)Use the boomerang in the minor range possible so it has more possibility to hit twice the enemy or enemies.
3)Use spell shield as an pre-protection, for example if a enemy is chasing you and that enemy have a skill of throwing or jump to you calculate the right timing to use spell shield so you can block it.
4)Always think that On The Hunt can be used to kill or to escape, and also to help the allies champion.
5)When you are pushing and you are destroying a turret, may sure that there is not enemies around the turret cuz if them deactivated ricochet so you get no problem with the turret by hitting the enemy when bounce.
Interesting fact 6) Most you are thinking why phage or frozen Mallet? This is because with any of THIS ITEM + ON THE HUNT you get Super Speed when you attack, Sivir and allies attack so fast that you can barely see it the attacks.

The Items explanation:
1)Meki pendant with potion to farm and lvl up in very early game
2)now people will wonder why ninja tabi, well lets said that sivir's passive + rune of dodge + the ninja tabi will give you a total of almost 50% dodge that is like almost the half chance of dodge a skill.
3)Blood Thirsty is good for mid game because the effect will give you a bonus of damage and a bonus of lifesteal
3)Then with stark fervor you will have a great % of life which will help you to survive in core game
4)Use Omen to have a little armor and also active the skill so save you, and you will survive a little longer in team fights and normal fights.
5)Guardian angel will be really useful almost for late game because everyone will be strong and in order for you to survive in team fights is to revive with Angel.
6)Last whisper for more damage and armor penetration to kill or destroy turrets very fast and easy.