No. Please do not wear a full costume.
The outfit is connected to a character you really like from something (anything). You can do as much or as little as you want. Some examples: Superman- blue suit with a red shirt and yellow Superman tie, or any suit with a superman tie, etc. Batwoman- black dress or suit with a red bat necklace Yoda- brown suit or pants with a green dress shirt
Absolutely not. This is meant to be fun. If you won't enjoy it, don't feel obligated to do it.