Bellona forever

By now you are ahead of people from kills and farming minions, make sure you are at the front of the team fights, with your passive and ult will make sure the enemy dosen't push to far and the other are their for your back up.

Once you have your first three items online, you can start wasting people. Also make sure your scourge is at 5 and mainly attack witht hat. attack speed allows you more hits, while between gauntlets and scourge you have insane life gain. Also don't be afraid to go and solo the gold fury at this time, or around 16, with stone of Gaia go solo the fire giant.

This build is weak early game until you get the devourers gauntlets online. For early game, hold back and just farm minions, if the enemy engages you, don't be afraid to attack them but don't push, you might be ganked. the gountlets will allow massive lifesteal without relying on scourge to get it.

The ninja boots helps with movement speed, which with her passive greatly increases chase and escape, and attack speed which helps your healing. Devourers gauntlets gives her life steal, which allows for you 2 to also gain her life and not just with scourge. Executioner gives even more attack speed and if your opponent is building defense, helps you ignore some of it. You will notice that Bellona suffers from mana regen, stone of gaia helps with the mana, and helps sustain you even more. By this time, you could solo the fire giant, which would be a nice surprise for you team. Also this is entering end game, so hence the runeforge hammer and breastplate of valor for more defense, power, and cooldown reduction for you ult.