Plagues

I understand why God plagued the Egyptians, but I don't understand the reason behind some of the specific plagues:

Plague 1: I get why God turned the nile into blood- kills the major source of water
Plague 2: Frogs? why frogs? they don't seem like an evil creature
Plague 3: Gnats- those can be annoying
Plague 4: flies- isn't a Gnat a type of fly? so why now just flies in general? seems a little redundant
Plague 5: disease affecting livestock- that makes sense, kill the food!
Plague 6: boils- eww gross, surprised that didn't work
Plague 7: hailstorm- well with all those boils I would welcome a clearer upper (please kill all my livestock!)
Plague 8: Locusts- Wasn't all the crops wiped out by the storm? what is there to destroy?
Plague 9: Darkness- now we're talking!
Plague 10: Egypt's first born- that will do it, kill people!