For any bible study, always need 3 steps: observation, interpretation, application. No application can be concluded without enough observation.
So to observe, what does oil represent?
It is the only difference between the fool and the wise, it cannot be transferred or borrowed as it is an individual matter, it costs the fool being shut out.
Oil = the indwelling presence of the holy spirit
There’s coming a day when the door of salvation will be closed.
God say “Truly I tell you I don’t know you.”
“Know” indicates that the salvation is about having a personal relationship with Christ.
So to apply, the wise bridesmaids have extra oil filled, then how do we always be filled with holy spirit?
A spirit filled life is controlled by the spirit (just like a drunken filled with alcohol is controlled by the alcohol, an opposite controlled case), it is in each single day, learn to submit, let the God be in charge of my life.