The gemstones you need is Black Tourmaline & Aragonite. Black Tourmaline helps to release fear and to increase self-confidence. It is a stone that helps you become comfortable in your body and your being by its grounding properties. It is helpful in releasing victim energies as well as protecting you from being victimized. Aragonite also boosts self-worth and confidence. It also helps to relieve stress and balance the nervous system.
Of course, there are many different causal factors to a lack of self-esteem and confidence. It can range from lack of self-love, from having experienced devaluation at a young age and other types of unresolved childhood issues. There are also many dynamics and emotions that cause us to develop a negative image of ourselves, including comparing ourselves and our bodies to others and not feeling we measure up.
I have found that clearing the unresolved energies and imprints carried in the energy field is highly effective at releasing feelings of low self-esteem and increasing confidence. You can find more information on healing these energies here.