There is a retailer selling the Babylon 5 station uniform - and Minbari and Narn headpieces. If either of those tickle your fancy, take a look here . Johanna has picked up all of these patterns and has put them on her 'easy enough for even me to sew' list. Play with altering sleeves, layering contrasting garments, pleating a wide shoulder, rather than gathering it, etc. Muslin is cheap, but can be brittle.
Fabrics can be sheer, smooth or slightly textured - heavy textures are out.
Contrasting trim is present on many garments, particularly the top layer. Surcoats and sashes are popular. Johanna didn't see a lot of silver or green while looking at pictures, so you might want to stay away from those. They won't be nearly as ornamented as what is seen on the show, but the garments will be distinctive enough to evoke the correct mood. If you want something with a lot of fabric, take a look at Simplicity 8725 - the sleeveless surcoat in particularly.