You must be competent; you must seek to be more competent. One of the problems that we have today in the world is that confident people are not competent and competent people are not confident.
Philippians 4:13
I have the strength to face all conditions by the power that Christ gives me.
So, if you Will succeed, you must seek to possess both qualities. You can be competent now and lack self-confidence or you can be confident and lack competence.
However, if you wish to be effective in leadership, you must be strong both ways.
It is painful to find a very confident but empty person stand up to talk only to blurt out foolishness and display sheer incompetence.
There are people who will step up to a platform because they are confident, only to begin to say nonsensical things while there are competent people sitting down and complaining.
A person who intends to acquire and grow in the leadership life must strive to possess both confidence and competence,an example in the person of 
The truth is that no nation will rise to the peak of its potentials if competent people don‘t develop confidence to come forward.
Fight everything that wants to attack your confidence, destroy it before it destroys you.
For the spirit that God has given to us does not make us timid; instead, his spirit fills us with power, love, and self control.2 Timothy 1:7
There are all kinds of things that can supply you competence; further education, attending a training, private study, receiving coaching from someone who is competent in the area you seek to get better at, acquiring a mentor, attending conferences etc.
You need to labour to be more competent than you are now. You can always be more competent, strive for mastery.
So, get competence, get confident and keep getting better. All through life, you will need to work on getting better at both.