Should I make a toile first?

Yes — for anything fitted, anything in expensive fabric, and any pattern you have not sewn before.

A toile (or muslin) is a test version in cheap fabric, made to check fit and proportion before cutting the real thing.

What it tells you that measurements cannot. Where the waist actually sits on you. Whether the shoulder seam falls in the right place. Whether the neckline gapes. Whether the proportions suit you at all — a dress that looks wonderful on the pattern envelope can be simply wrong on a different body.

How much to make. Not the whole garment. For a fitted bodice, the bodice only, with one sleeve. Skip facings, hems, pockets and closures — pin the opening. Half an evening, not a weekend.

Use fabric with similar weight and drape. Calico for a structured cotton dress. A cheap jersey for a knit top. Testing a drapey viscose dress in stiff calico tells you very little, because the drape is most of the design.

Mark your changes on the toile itself, in pen, then transfer them to the paper pattern. That paper pattern is now yours and every future version starts from it.

When to skip it. Loose garments with lots of ease, patterns you have made before, and anything where the fabric costs less than the evening.