how to join large existing group of friends?

recently i stopped being friends with my other 2 friends, as they talked bad about me and everyone else. this was a great decision in my opinion because asides from talking bad about me since they talk bad about everyone, lots of people assumed i didn’t like them or talked bad about them too (this was never the case i never disliked anyone). all this aside in my grade theres a huge group of girls who hang out at breaks that consists of around 9 people (they’re sort of the popular group i guess). i decided to try to hang out with them and its been going pretty good so far. i sat with their table group in class for a week and they were nice, i’m pretty quiet and they usually just play iMessage games (i would too but i dont have a phone hahah cant get one till next year) but when they do make conversation i try to engage and they usually respond and add onto what i say a little. its a little odd though since when i talk they all look at me wide eyed LMAO off topic though the point im making is i dont know if they hang out with me because of pity that the other girls talked bad about me (yeah they know everyone does) or because they dont mind me floating around them. there’s four girls of that group in my class whom i sit with. at lunch all of them sort of come together and just browse on their phones (once again dont have one so i just scribble on my hand or do something of the such) and sometimes they show eachother memes or tiktoks and i laugh along with them hoping to fit in a bit more. i want to get closer but find myself struggling to join the conversation, since they keep referencing things that I–not having been there– don’t get. or places that i havent gone to, or plans from last year.

TL;DR: joined a friend group of 9 due to old friends talking shit, cannot figure out if they enjoy being around me or its out of pity. i have difficulty engaging in conversation sometimes, help!