Suits - when you are buying them, do the test where you grab a handful of the fabric, close your fist, and count off 10 seconds. When you release your hand, the better fabrics won't show a wrinkle.
Wool can be wonderful, and there are lighter weight wools even for summer. Sometimes blended with the polys.
Rather than a straight skirt, pleats that are sewn down but stop before the crease across when you sit can be good. The skirt just doesn't bend in that area, but rather pulls straight from the bottom of the sewn pleat.
A-line skirts work somewhat like the pleated skirt.
Wearing a slip under the suit skirt helps a little as the slip catches the first of the bend. Body warmth, a little perspiration all contrive to set that crease, and the slip blocks it a little.
I agree with the recommendation that the suits be lined. It helps.
A looser fit helps.
Hang them up as soon as you get home.
It seems to be a whole bunch of little things. The fabric is part of it, but cut and care and other things play a part.
Since I'm happily retired, I can't name brands any more but I'm sure somebody else here can help with that.
The good ones are expensive. Roughly what guys spend for good suits.
Romelle