Keep it in this container for the time being. Seedlings of Ginkgo biloba are vulnerable to root rot if the compost is too wet. If you repot this small seedling into a bigger container the danger of the compost being too wet is significantly higher. Fertilization is not necessary in my opinion.

This looks amazing! I wish I had a ginkgo seed so I could give it a shot.

You could keep it in the same container if you lifted it and added more potting mix. All plants growing in a soilless peat, coir, or bark based medium will require fertilization at some point.

You may want to consider deciding what kind of medium to grow your bonsai in so that you can switch it over soon.

Two of my favorite specimens were ginkgo grafts....very enjoyable and rewarding to work with.