Savannahs are high energy cats, with loads of intelligence, but are not necessarily destructive. If left alone for long periods though, a Savannah might find things to amuse itself with what may not be an activity you would choose for them. It is important to make sure that they are well-occupied, possibly with another companion pet, or that your house is well Savannah-proofed.
It is also important to train your pet in the way you would like it to behave. Dissuade and distract from inappropriate behavior and give them suitable toys to expend their energy on. A Savannah is not simply a gorgeous animal, it is highly interactive and needs time with its humans. If you do not have much spare time between your job and activities, then a Savannah may not be the right breed for you.