Anxiety advice

My best friend has invited me to one of her parties for the first time which is this weekend. I usually enjoy parties, although I don’t go to many, but this time it’ll be at a venue with quite a lot of people going. The only issue is that there are 5 different worlds of mine all colliding. First is me and my best friend (who invited me), second is me and an ex best friend from college (who’s also “friends” with my best friend), third is me and a close friend from secondary school (who I don’t see often anymore), fourth is me and a close friend from primary school (who I haven’t seen yet alone spoken to in over 10 years) and fifth is me and a close friend from my dance school (who I haven’t once again seen nor spoken to in years). I’m not the most confident person but am always friendly and try to make conversation although I am really anxious and awkward about social interactions with people I’m not comfortable with. Im just worried about how to interact with so many different people from my different “worlds” who some know of each other, others have no clue who the other is and how to deal with it all colliding. My ex best friend has asked my best friend if she’s going to the party so we (me and my best friend) believe she will want to stay with us as she said she doesn’t want to go alone. Me and my ex best friend ended civilly and although deep down I don’t believe we enjoy each others company, we will always act the opposite to each others faces. The one time me, my best friend and ex best friend have hung out together (when I was still close with her) the vibe was very very tense and uncomfortable and I got the impression my ex best friend viewed her friendship with my best friend and my friendship with my best friend as a competition, so we have avoided hanging out together since. She doesn’t know I’m coming to the party yet as I feel like that might make her want to come even more as she won’t want to feel left out but. I’m also expecting my close friend from secondary school to expect me to spend time with her, bear in mind my ex best friend and close friend from secondary school say they don’t like each other, though they’re both the type of people to act extremely chatty and outgoing to one another’s face so it isn’t awkward. I’m very anxious and nervous about the party and was questioning not going to prevent the anxiety but I feel like I’d be missing out especially considering it’s the first party I’m going to with my best friend and i know lots of people going. Can someone please give me advice on any ways of dealing with the anxiety, and maybe some tips of conversation starters that I can use, or maybe a mindset that might help? Thank you.