Vegas attire is some of the most diverse I have ever seen. Flashy, tacky, sparkly, barely-there, frumpy, you name it, you’ll see it. This is one of the few places where anything goes. I mean anything.
I personally like to have fun with my wardrobe when I go to Vegas. I actually have a section of my closet for my “Vegas clothes”. This section includes spike-heeled boots, sequined shirts, sassy high heels, and even small fashionable purses that can be carried easily but still accent a chic wardrobe. I still wear regular casual clothes occasionally, but this is definitely the place to come if you want to get a little more flirtatious or fun with your clothing. One of the things that gets me is when I see women in spike heels that look like they have been walking all day. Remember that the Las Vegas strip is long, and casinos are large. If you are planning to stay in your shoes all day, make sure they are relatively comfortable. If you are just going out clubbing or to dinner for a couple hours, by all means wear those heels.

Many women choose to dress like J-Lo at the Oscars with their low cut or bust enhancing get-ups, especially in the summer. Other women wear tennis shoes and fanny packs. I, personally, don’t advise the fanny pack look, but it is fairly common. Not as common as cleavage by any means, but still normal. If you don’t have any hip clothes and you want to dress up sassy, there are plenty of boutiques that sell them in Vegas.

Men vary as much as women in the fashion department. Some men look like minivan driving, soccer dads from the Midwest, while others look straight out of a fashion magazine. Anything goes.

So check the weather in advance of your trip and pack what feels comfortable to you. Believe me, you will blend in no matter what you choose.
Remember that if you plan to go to a nice dinner, restaurants may have dress codes, such as no tennis shoes, no jeans, or dresses / dress pants required for ladies. Be sure to check or just bring a semi-formal outfit just in case.