Level I does not provide enough information for the day trader. Level 1 is price without the underlying activity.
Level 2 and the tape is also an indicator of price movement between the buyers and the sellers. (bid and ask).
The shares being bought and sold are shown in multiples of 100
Level 2 shows the bid and ask, the time and sales shows the price of a stock is being bought and sold at. Level 2 shows the cycle of price