Well, if you got a few kids and only buy 1 toy, they will definitely fight for it. You can either choose to buy for all of them or don;t buy at all. I educate my kids to share by buying for all of them. You must buy the same else they will also fight. Taking the opportunity to teach them the power of sharing which is very important.
Had heard from some mummies that U can buy each child the same toy so that they won't fight and in fact, they will learn how to play together as there are no differences. However, that is also provided that you have enough $$ to spend on the kids. Alternatively, you can always gather them to do handicrafts together.