There is no excuse for anyone not to learn drawing Clothes Design Sketches even for themselves. The reason is pretty simple: sometimes we need tailored clothing for particular reason. If you have been tailoring the same model of clothing, you urgently need learning to draw sketch and, for sure, inspiration.
Even though you are not artist, still, it is totally fine for you to design your own clothing. Thus, prepare pencil, drawing paper, and eraser to start working on your Clothes Design Sketches. Next, what you have to do is simply draw the clothes that you want. It is okay to draw it big enough if you are not sure others will know about the detail. It should be clear enough at least for the tailor to know.
As newbie and as you draw the sketch simply for the tailor to know what dress you want, you do not need to learn types of stitch. Actually, when you are learning to draw Clothes Design Sketches, you also need to learn to draw the stitches too. However, you do not need to for the reason we have agreed before. But in case you want to show the stitches, it will be better if you draw it also, or just simply tell the tailor what you want to do. Good luck!