Clothing from the Elizabethan period was diverse, as it encompassed several decades and many cultures. Clothing from the period varied by economic status, as well. In fact, there were laws that prohibited people from dressing above their economic station. When choosing a costume from the time, you may choose from a basic peasant style to the elaborate dress of the nobles. You might search for patterns in period designs or use some modern patterns with alterations to achieve your desired look.
Design the undergarments. For the time, the basic undergarments were shirts for men and smocks for women. A smock was a T-shaped garment with long sleeves that came down to the knee or hip. It usually had a square neck. The sleeves may be straight or made to taper down into a cuff at the wrist. A man's shirt was usually rectangular and came to the thigh. The shirt's opening was to about the middle of the chest and fastened at the top with a button or a tie.
Make the bottom of the outer dress. Breeches were what men wore as trousers during the Elizabethan age. These generally came to the knee where they closed with a button or a tie. The opening at the top was usually a triangular flap that buttoned or tied. You can use a modern trousers pattern and shorten it to taper at the knees. Women's skirts are ankle or floor length and full, not fitted. You can use elastic or a drawstring for the waist.
Construct the top of the outer dress. Men wore doublets or jerkins over their shirts. A doublet is like a sleeveless jacket with a standing collar. It was wide at the shoulders and tapered at the waist. Jerkins were thigh length, vestlike garments, usually made of leather that closed in the front with buttons, ties or a belt. Women wore bodices or corsets on the top, which were supported by bone and designed to flatten the breast area, not shape the waist. Bodices tie in the back and do not need to be extremely tight, but should compress the body only slightly.
Remember that the higher the economic class of your costume, the more elaborate it will be. Peasants wore simple, unadorned garments, while middle and upper classes had numerous ruffles and embroidery on their outfits. Upper class women wore numerous underskirts to shape their skirts and make them full-bodied. During the Elizabethan Era, outer sleeves were a separate clothing item, designed to button or tie inside the armholes of garments such as bodices and doublets. Keep this in mind if you want your costume to be accurate to the period.