Decide what you're dressing for. School? Work? Party? Show? Get-together? For example purposes, I'm going to say school.
Pick an article or accessory you absolutely want to wear. I chose this dress because it's finally warm and I've been dying to wear it all winter. It doesn't have to be a dress, sometimes I pick a hat!
Decide what limitations you have for where you're going. Do you need to be more conservative? Can you be flashy? Is wearing a hat appropriate? Etc...
Since I need to stay in school dress code, I had to pick a cover up for my shoulders. I chose a white denim jacket to structure the flow-y dress.
After you have the main part of your outfit nailed down, you have to accessorize. Try to grab a couple items to start that match your colors, and usually stay away from mixing gold and silver.
I chose this necklace after comparing a couple because the grey was a nice middle ground between the navy and the white. Also, I made sure the silver matched the buttons.
For shoes: decide... Closed or open toes? Should you wear flats, or heels? Match or complement the color, but you might have to try a couple pairs before it turns out "right".
I chose simple t-strap sandals because I have to walk to school and it's getting to be warm outside.
Finished product with my sister modeling. This is a more simpler and preppy outfit than I usually do, but the thought process I used is the same.
Sometimes it's discouraging to not have the pieces necessary to make the outfit you want. Just start swapping things out of what you already have, and magic could possibly happen. ;) Good luck!