Standard poison auto-attack

Lunara is squishy, so you should always attack and move.

When lvl7 with  Splintered Spear  , Noxious Blossom   > auto-attack > Crippling Spores   to spread poison  on enemy heroes

Thornwood Vine  ,  Greater Spell Shield  or  Star Wood Spear  to play safe

Lunara is good to kill bosses/objectives like the immortal, the golem etc (with  Nature's Culling  )

Lunara is a goddess against burst healers like Uther.

If possible, try to reach 3 stacks of poison on an enemy then switch to another target to apply stacks. But don't forget to refresh the duration on the first enemy with one auto-attack from time to time

Move, move and move again during team fight : don't forget that you are an heroic mount.

Did I forget to mention to move after attacking an enemy ?