Plain sweaters are one of the best clothing item for college goers. They are versatile & keeps you warm. Try darker colors first - black, dark grey, navy, etc.
Hoodies look really sexy especially plain ones. They are easy to pair with jackets, coats, etc. Make sure they are above 350 GSM.
Dark jeans are really versatile and goes well with winter clothing. Darker clothes also absorbs heat, hence making the clothes warmer to wear.
Turtleneck & highneck both are really good for layering under jacket, suit, coats, etc. Go for black, white or off-white color first.