to the best of your ability but your best is less than adequate for the situation.
the bare minimum
Scenario 1
Person 1: What are you doing?!?!
Person 2: MY DOODLIEST
Scenario 2
*watching cat fail at catching a bug*
Person 1: She's doing her doodliest...
When you're doing your best but your best isn't very great to begin with.
I'm doing my doodliest.
Do your doodliest.