There are different postures of Ganesh idols and sitting in one leg folded (the lalitasna) is one of the best for you. You need to have either standing or dancing one for your home. It is best however to avoid using the dancing one in the car as it signifies destruction. Similarly, reclining the same is best avoided as the same is a position of rest and relaxation.
As a result of the same, choosing the standing one is best for offices. It helps you to welcome guests. Thus, the best possible position is the sitting one that is both relaxed and reassuring. This assures that you achieve the best results for your needs and expectations. This brings only prosperity and happiness for you.