What do people talk about? I always find it hard to think of something to start a convo on.

The weather.

Starting a conversation is like priming a pump. You have to put a little water in and start pumping before it starts moving water for you. Put out anything to start a conversation, just try not to make it creepy. Usually, normal people will respond in some way if you start talking. Rude people will not or will walk away. That is, also, a way to determine if they are worth your time or not.

People like to talk about themselves and what’s going on in their lives. So you can start a conversation by asking a question about the other person.

Start out with a compliment, but not an over the top false compliment. Oh, your nails are pretty, who does them? Cute shoes!
As @seawulf575 said, a normal person will come back with a an answer, a rude person will not, in which case you want them to move on anyway.

@gondwanalon is right.

Depending on the situation, it could be a mutual friend or if an event, how are you affiliated with this organization?
Women generally love to talk about kids/grandkids and animals, men generally love to talk about sports or stocks. Good starting points anyway.

You don’t need to talk to people. Find your own hobby and only talk to people that participate in said hobby. Keep things on the surface with outsiders and appear friendly but don’t let people in.

“Hi, Amy I’m Raya nice to meet ya!” I like your hair how do you get it to look so nice? Oh, those shoes are to die for. That outfit you have on is lit, were did you get it? etc…

Sometimes, something simple like “did you have trouble finding parking?” will open up the other person to start chatting. At a party, a question about the food “did you try the chicken wings? So good!”