Assuming, of course, that you can find fabric that you like,one way to go if you can't afford custom and don't want to sew a cover is to buy one ready-made and alter it.
First, check the measurements of your sofa or chair (length from front to back, side to side, and top to floor) and then go shopping. Internet preferred, of course, since we all want to save gas. Check the measurements of the ready-made cover to be sure it is at least as large as your measurements and possibly a little over.
When you get it home, put the cover on the chair or sofa, take a good look, and decide if you want it smaller somewhere. Do the same thing with the cushion cover(s). If there is cord in the seams, you will have to open them at this point. Turn the cover wrong side out and pin the seams that need taking in. Do it with large stitches first, so you can tweak the fit if you need to.
Note: if you want to do this by hand, just be sure that you make "back-stitches" every inch or so, to keep the stitches from pulling out under stress. Sew the seams with LARGE machine stitches at first.
After you have a good fit, replace the cord in the seams if there is any, re-sew and trim the seams. Serge them, if possible. Most ready-made slips are in less than wonderful fabric, and you don't want any fraying in the washing machine. Some people even bind the seams by putting strips of bias tape or something like it over the seams.
If this system works for you, please send us a picture of your results. Wing chairs are the hardest, but if you Google "wing chair slipcovers" you will be surprised how many sources you find!!!