"When they awake, dote on the first thing they see" - Please explain this line from A Midsummer Night's Dream.
This line, spoken by Oberon to Puck, refers to a love potion that Oberon wants to put on the eyelids of the sleeping Titania.
"Dote" means to be overly affectionate.
What Oberon is doing in the passage you cite is explaining what the potion does. He tells Puck that the love potion will make Titania fall in love with whatever she first sees when she opens her eyes again.
As it happens, Puck ends up putting the potion on Lysander while Oberon puts it on Titania. Lysander ends up in love with Helena and Titania with Bottom.