One of my winter projects was to make simple "starter kits" for two ladies starting out in Revolutionary War reenacting. Neither is sure just how often she'll make it out, and we wanted to have a versatile outfit that was authentic, easy to wear, and inexpensive until each decides if she wants to commit to stays and a gown or other fitted garment.
So--for each, I chose to make a bedgown-based ensemble that will be fine for working in camp and getting a taste of the hobby.
I based the ensembles off period images that show women, clearly "unstayed," wearing a bedgown/shortgown, often with an apron.
Louis Philippe Boitard, 1738-1763 A Fisherwoman, Hands under Apron, Yale Center for British Art. Love her red kerchief. Visibly not wearing stays.
Detail from The Mutual Embrace by J Collet, 1774, print, original in British Museum. Happy dotted shorgown.
Detail from The Elopement, print by J Collet, 1764. Not the most attractive lady...but her outfit is a super-simple one to copy.
Each lady received a shift (or already had one), two petticoats, a bedgown, and an apron. I used the shortgown pattern I've used before, with a few adjustments to increase the length a touch.
All items were made of linen. The ensemble pictured below (excuse my messy sewing room corner) is made from fabrics from fabrics-store.com (light blue Meadow for the bedgown, Olive and Navy petticoats) and Wm Booth Draper (the blue check for the apron).
Not pictured, a cap and a kerchief for the neckline.
To DIY your own first time out ensemble (all of which will also be wearable if you do decide to make stays and more fitted garments later!), consider:
Shift: Pattern from Kannick's Korner or from the gridded extants in Costume Close Up or Fitting and Proper.
Petticoats: No pattern is really needed to make 18th century petticoats--they are basically large, pleated rectangles. I like this tutorial from Koshka the Cat or this one from A Fashionable Frolick Both are pretty much the method that I use for my petticoats and the ones pictured here.
Apron: The apron is, much like the petticoats, basically a large rectangle gathered or pleated and stitched into a tape waistband. Hem all three sides, then pleat or gather to length and attach tape for a waistband.
Bedgown: There are many styles of extant shortgowns or bedgowns, and many more variations exist in period images. How I make mine is detailed here. A few commercial patterns include this very basic shortgown and this slightly more complicated bedgown. I can't really vouch for the ease of construction or authenticity of either pattern as I've not used them myself.