Do you need to have your own minis for DnD? Ive only ever played with online friends and would like to maybe join a campaign with some new people.

It totally depends on your D&D group. Some groups don't even use minis at all and go with the "theater of the mind" while others prefer to use minis to make combat easier to represent. Just check with your DM.

If the game uses minis, every gm I've ever seen brings extras. Don't worry. You'll be covered.

People might have some you can borrow, but it's a good idea to bring your own.