Missions are EXPENSIVE, and not just the portion you pay to the church. There are required immunizations to get, luggage to be purchased, scriptures and books for personal study, and clothes for 18 months that can also be pieced together into several different outfits, not to mention all of the extra expenses for living and personal care. With all that in mind, it can sometimes be hard to find cute clothes that you would enjoy wearing for 18 months that can be interchanged with other clothing and that don't cost a fortune.
My first piece of advice is to search your closet and see which clothes you can bring with you on your mission. With sisters, the shirts must be high enough so there is no cleavage, and the sleeves must be long enough to cover your garments (cap sleeve length). Skirts and exercise/service shorts must cover your knees in the front and back when standing or sitting. T-shirts for exercise/service can have logos, but they must coincide with the teachings of the church (so a high school or EFY T-shirt would be fine, but a Bud Light T-shirt, not so much). Other than that, there is a wide variety of clothing options for sisters that are cute but also mission-appropriate.
After you've found some skirts, dresses, and shirts that you feel are appropriate, decide what is missing and what you still need to buy. It's recommended that you bring 3-4 dresses, 8-10 skirts, and 12-14 shirts with you on your mission, in addition to a few T-shirts, a couple pairs of shorts, and a pair of jeans for P-days and service. Some sisters prefer to bring more than this, so it's really about what you have the space and weight for in your suticase. I probably have about 20 shirts that I'm planning to bring, but I'm also using space bags to help fit all of my clothes.
Shop with specific items in mind. If you have a lot of plain tops, look for some nicer blouses. If you have lots of patterned skirts, try finding a few solid ones that you can pair more shirts with. When deciding which stores are best, I personally love thrift shopping. The clothes are always cheap and if you're willing to go back frequently and spend some time really looking, you can usually find what you want. A lot of times clothing from Deseret Industries (DI) isn't always the cutest, but you can find nice things if you're willing to take the time. Also, pay attention to sales in nicer stores and dig through the clearance section. If you notice Mikarose is having a sale on everything in the store and you happen to find a dress in the clearance section that is further discounted by the sale, it will be much more affordable than if you stop by on a normal day and hope to find something.
My last piece of advice is to ask some recently returned sister missionaries (or sisters serving in your area that will be returning home soon) if you can have some of their clothes. Most sisters will leave a lot of their clothes behind on the mission or will be willing to donate to new sisters. Good luck and happy shopping!
