Hi!
From my short experience with bonsai I would let it grow just as it is for now.
The substrate seems to be adequate so I would let it grow and apply fertilizer.
Let it grow until the base of the tree (the nebari) is big enough and from there I would hard cut it and start building from there.
What you should focus on now is maintaining health of the tree and make sure the basics are there for a healthy ficus,
Second step will be the diameter of the base, and for the base to go bigger you need more growth. The style or look of the upper branches doesn't really matter for now.
Just in case, I would not remove that low branch as it will help the base to grow thicker.
Hope it help