First thing, welcome to cosplay! My first costume was actually Lenalee and that was fun!
Now, if you want to cosplay as Road, do whatever costume you like. You might also want a Relo umbrella with you to finish the look, wear either black or purple stockings. If you can sew, I feel like some of this costume can me hand made. Like making a skirt using a circle pattern and adding lace in the end.