Hmm I think it helps if you recognise that these people are merely the parents of your child's school mates and are unlikely to become your friends.
If some do, then that's a bonus!
I think I'd start off with what you need for your DD's sake. Ask if there is a contact list or something (FB page, Whatsapp group, ...) so you can get in touch with other parents to potentially arrange playdates. Then when the time is right, ask your DD who she likes playing with and invite that child for a playdate.
You probably find it nicer to be able to engage in small talk at the school gates than to stand quietly by yourself, so to achieve that, try approaching one person at a time, introduce yourself (hi I'm x's mum, we're new to the school), ask about their children. Usually that will get people talking.
It's entirely possible that you will find the school gate environment unpleasant and will end up just dropping off/picking up and avoiding all social encounters. But it is worth giving it a go - some people may be really nice, just settled in their routines from nursery times.
You can also try the PTA or consider volunteering at school.