If you're trying for a historical look, research very specifically the colors, fibers, patterns, and weights of the fabrics that were in use then.
A heavy synthetic upholstery fabric cannot reproduce the look of a fine silk brocade. While it's possible that 16th-century English folk could have had access to bright teal silk, would they have worn it? And paisley was only fashionable in certain times and places and on certain types of garments.
The wrong fabric choice impacts the look, of course, but more than that, it can make a costume bulky and uncomfortable.
Movement and drape are also an issue. For example, an Elizabethan gown needs a fabric with body rather than something limp and 'drapey', but an 1810 evening gown must be gossamer and fluid.Melanie Schuessler
Melanie raises two issues here. Clearly, if you’re going for historical accuracy you can’t just use any old fabric. It takes time and research to get it right (but never fear, you can guarantee that someone, somewhere, has already done that research for you.) Even if no-one who sees your costume knows the exact ins and outs of 1790s cotton prints, the right one will just look right, feel right, and give you extra confidence when wearing your gown – which gives you the “wow” factor you need.
But even if you couldn’t care less about historical accuracy, you still need to consider what makes an appropriate fabric. The book or pattern envelope you’re using will give you some ideas, but further than that, consider how the costume moves. Does it need to be voluminous like Queen Victoria’s skirts, or does it need to be fluid, aqueous, like the gown of a Grecian goddess or 1930’s screen siren? Look for fabric in a bricks and mortar store, where you can get your grubby paws on it and play with it, wrap it around you, hold it, drape it, get to know it. Does it feel right for this project? Later on, when you’re familiar with fabric names and the qualities of each type of fibre, you’ll be ready to play the lottery of buying online.