Also,
if you need any help at all with the foundation garments, let me re-iterate some advice, some of which I know has already been said:
depending on the period you wish to represent will depend on how these garments are made.
either they can be armor in and of themselves like mine, or they can be little more than something to hold your armor on to.
For example, my kit is an "earlier period" representation. I'm an early 13th century Knights Templar. This picture is from Osprey publishing on the Knights Hospitalier, but the kit is very similar minus the color of robe and cross:
For my period, we have basically two padded garments:
aketon underneath the mail (fig6 in the drawing)
and
gambeson over the mail that can be sleeveless (fig9 in the drawing)
For my kit, I have an aketon underneath the mail that's about 1/8" thick and a 1/4" thick gambeson on over my maile. I don't have my mail done yet, but I was able to borrow a friends to make sure the gambeson fit. Silly me, like others here that was actually the first garment I made, and it was made way too large. Basically my first "aketon" became my gambeson.
Also, my soft armor is made out of pure cotton, with cotton batting, and machine stitched. I fight in it, and I sweat in it ALOT. So I wanted it machine washable.
My aketon has 1" channels for more stiffness
My gambeson has 2" channels and two layers of batting for more loft. I made all the patterns myself to me. If you need or want help with this I can help out if you'd like.
Beyond these garments, with the inventions of more plate, it evolved into the "pourpoint" like Sir Ian has, that "Tailoress" over on the armourarchive has made a beautiful pattern for. This is more a 14th century period garment, think 100 Years War, "Cantebury Tales," "A Knights Tale," the Black Prince Edward, etc etc.
Beyond this garment, it really became more of something just to point your armour too with little or no padding within it. This is far beyond my researched time period and something I know little about. However, there are plenty of us here that do know this very well. THIS is the period of the "Knight in Shining Armour" and a ton of plate everywhere, like in Sir James' Avatar.
I hope this helped some for your padded garments. And like everyone else has said, this really can define the rest of your kit, and make it far more comfortable and forgiving, or miserable to wear.