Your customer wants a silk dress, but you have to measure the mannequin, cut the fabric, and sew every piece before you can even see the final result. Dressmaker puts you behind the sewing machine and lets you handle the whole process yourself from the first measurement to the finished outfit.
Check the customer's order before starting. The Dressmaker game then takes you through the whole outfit, from getting the size right to handing over the finished clothes. There is also a budget to deal with, so picking the most expensive fabric every time isn't a particularly good idea.
Take measurements: Get the mannequin the right size for the customer. That's the first thing to do.

The sewing is where Dressmaker gets interesting. You cannot simply pick a finished dress and hand it over. You have to make it piece by piece.
Cutting the fabric badly can leave you with more waste, while a poorly guided seam can affect the finished garment. The sewing machine also gives you some control over how carefully you work. If you do not want to worry about every little movement, the sewing assist mode makes things easier.
Once the main pieces are together, you can spend time on the smaller details. A few buttons or some lace can entirely change the final outfit.
Not every order has to be perfect. You can follow the customer's brief and build a good reputation, or deliberately make something strange and see what happens.
Managing your fabric costs also matters. Expensive materials may help create a better outfit, but spending too much on one order can leave you with less money for the next one. Between measuring, cutting, sewing, and decorating, Dressmaker gives you plenty to do before the finished dress ever reaches the customer.