Unless it is a high-end, luxurious casino, you can wear a smart-casual outfit and be safe with your choice. We assume that most people will visit casinos that don’t have a strict dress code, but it’s expected from the guests to look their best. Therefore, it’s always better to be more smart than casual, but don’t pressure yourself to wear something uncomfortable. At the end of the day, this is still a fun night with your friends and you should wear something that makes you feel good about yourself.