"I want to build a Star Wars costume, but I have no idea where to begin!" There's no right or wrong way to begin a costume build, but there are two key factors that will determine which costume you can make- body type and budget. Once you figure out both of those factors, you'll be ready to move onto the next phase of creating a costume.
Body Type
First and foremost, The Dorky Diva is a non-discrimination zone. This segment will not be criticizing shape, size, or anything that makes you special and awesome. Each body is different and beautiful in it's own way! With that being said, body type is a really important topic to discuss when choosing a costume.
It's imperative that you understand your proportions and curves to know what costumes will fit you and which costumes may need to be modified. For example, a fully armored costume (stormtroopers, clone troopers, etc.) would not work for my body type because I am not tall enough to have accurate proportions. My short torso and legs don't leave enough room for the chest plate, ab plate, thigh, and shin armor of a fully armored costume to fit properly together. Here's a little cheat sheet to determine if you're a good candidate for a fully armored costume.
If you're in the 5'8" and under category and still want to create a costume with armor pieces, consider characters like biker scouts, TIE pilots, Sabine Wren, and Boba Fett. All of these characters have helmets, chest armor, and other armored pieces on their body while still mixing in a flight suit or under clothing of some kind to flex with their shape.