Diana is a formidable assassin/bruiser with high damage, great sustain from her W shield, and strong scaling into the late game.
Manage your mana carefully as Q can be costly, but leverage her strong all-in potential and defensive W shield to dominate the lane.
In teamfights, seek out key ultimate engages on squishy carries to turn the tide, but be wary of counters like Mordekaiser who can shut down your dive.