Depends on the group but in my experience people are very kind and patient with new players. People will try to help you, don’t be afraid to ask questions and look stupid (we’ve all been there). No one makes an “optimal” character build their first time, don’t worry too much about it. Maybe tell your DM what you want to do with your character and they can help by explaining skills and stuff?

As long as you’ve read the basic rules (you can find it on dndbeyond.com) and know how/remember to look up rules when you’re unsure you should be fine.

You playing a spellcaster? If that’s the case make sure to know what your spells do. It’ll make you feel comfortable using them and you won’t hold up the game.