Because I work nights, I have had to figure out a no-hassle basic outfit, because a couple of days a week I'm either asleep or on the school run. I don't have time or brain power those days to figure out full outfits!
In the winter/really cold days I wear yoga pants, long-sleeve tees and big jumpers (mens medium are perfect size for me), and I change into jeans to leave the house - I find that yoga pants are fine inside but aren't generally thick enough for outside.
In summer I wear leggings and tunic/skater dresses. Quick, easy to put on in the mornings and perfectly appropriate for leaving the house. In fact, the ease of these outfits has saved me on a couple of occasions when I've woken up late for something. Scenario goes like this:
Wake up, look at clock, scream! Run to bathroom, wash smelly bits, put on leggings, dress, cardigan. Thrust feet in shoes while waving at family, grab bag on way out door. Apply make-up/perfume on way to bus/on bus. Arrive at meeting place, down coffee and order more, revive friend from laughing fit having heard tale of woe.