The start of fall is tricky. It's not quite chilly enough for sweater weather, but not quite warm enough to extend your summer wardrobe. Also, if you anything like me you are probably over summer clothes anyway. Now that fall has officially commenced, it is okay to have this feeling.
In early fall the best way to transition is by making small tweaks. Put the brights away and darken up your color scheme. Swap your sandals out for booties. When the weather permits make the shift from light to heavier fabrics (wool, leather, suede, etc.). Change your prints from florals to plaids. It is the little variations that give you a fall look. You don't always need to be in a chunky knit sweater for your outfit to scream fall.