Pack your concert dress first. The most important thing you will be bringing on tour with you are the clothes you are going to wear while you are on stage. What you wear on stage creates the illusion and completes the package of style and image you are trying to express. Figure out how often you are going to have access to a washer/dryer or laundry service, and adjust accordingly when deciding how many concert outfits to pack. Keep in mind that your concert clothes are going to get sweaty and dirty quicker than anything else you wear.
Pack enough underwear. You can easily wear the same pair of pants or a shirt a few times before it starts to smell. But you can only double-dip into your underwear stash a certain amount of times. So be sure to bring plenty--enough that you only have to wear each pair once between laundry days.
Don't forget your toiletries. Nothing is worse than signing autographs for your fans when you have foul-smelling breath and a serious case of body odor. Grab all the toiletries you'll need and put them all together in some sort of tote bag. If you are bringing liquid products of any kind--such as body wash, shampoo or even mouthwash--be sure to enclose them in a sealable plastic bag. Since you are limited in what you can bring, it'll be a horrible day indeed when your shampoo explodes all over the rest of your clothes.
Pack emergency medications. There is nothing worse than having a bad case of diarrhea when you need to perform. You cannot always depend on your road manager or the venue to provide you with basic medications like pain relievers, antihistamines or stomach settlers. Come prepared with adequate amounts of these medications to ensure that you give your fans the best possible show.
Remember your day clothes. Use whatever space is left in your alloted amount of luggage to pack your casual clothes. These are not as important as concert wear, but then again, you can't wear your stage clothes all day. Be prepared for all types of weather. Make sure you have at least one short-sleeve shirt, one long-sleeve shirt or hoodie, one pair of jeans/pants and one pair of shorts, The rest is up to you, based on the space you have available.