I'm going to delay the time I go to a friend's gathering for an hour or two.
Why are you going to delay your arrival?
I hate parties, they are too noisy.
I see that it's overwhelming for you, but you should try to arrive on time if possible. It's rude to be late to an event that has a set starting time and can inconvenience the other guests.
I haven't decided yet.
If you feel that uncomfortable with the event, you could kindly let the host know ahead of time that you won't be attending the event so that you aren't a no-show.