I had Gerbils when i was young and i LOVED THEM, they were in a fish tank, filled with sawdust and they would bury tunnels etc, i was very obsessed with them.
One died quite suddenly and my big sister went and got me another, but it turned out to be a male, and before i realised, one was pregnant and i had to get another cage to keep the male in, and then i had to get another 2 cages to separate the males and the female litters when they were old enough until i got them new homes.
Safe to say It taught me a lot about caring for animals.
Apart from the pregnancy, the gerbils were great pets.
I had hamsters also, and i would say, hands down, gerbils are better....