Sometimes it can happen for me if I go to a group or gathering that people will get in these circles and be chatting but I may feel lonely or left out and not exactly sure how to enter in. How do you join dicussions when everyone else in in their circle? When I used to go to this prayer group I felt the same feeling of feeling isolated but I would also have trouble focusing in.
You need to purposefully position yourself in the group. Choose a target and invade his personal space, but within his line of sight, and in such a way he has space to back away. It helps if you look him in the eye while you do this. He will naturally step back, so as to regain his customary amount of personal space, and you're in the circle. Position your feet toward the centre of the group.
Have 60 seconds worth of questions or conversation to say to one member of the group. Either join in the existing conversation, or start your own questions/conversation. If you feel comfortable, continue the conversation you started. If you don't, go through your entire 60 seconds worth of conversation. Give opportunity for the target to say something. Listen. It's easier to listen than to talk. Try to ask questions about what the target tells. When your 60 seconds of pre-composed conversation expire, feel free to leave the group. You've made first contact.
Repeat the process, ideally with the same people, each gathering. By about the 4th or 5th time, the people you have selected will have grown accustomed to you, so will be more open to including you in the group. If not, these will still be more acclimatised to your presence. Continue the process with different people to make more friends, ideally changing the content in your 60 seconds of pre-composed conversation, and lengthening this as you gain confidence.