How do i improve my informal communication to help me bond with others

I an introvert guy who finds it difficult to speak in front of large audience or when put on spot. If there are 3 ppl and no one knows each other. I am not able to strike a conversation and if there is a girl i hold myself even further back thinking too low of myself and not to intrude anyone private space. However, because of this less initiative taking i have lost on good amount of people. They talk with me they would love to work with me. But i would be last one that they call , to party or chit chat. I feel let out but i know 50% of this brought by my actions of not taking initiative and striking a conversation.

Please guide me with your view. Given the platform is anonymous lest i would not have been able to talk this freely