In our country, every citizen has one vote. A scheme is proposed which allows anybody to buy additional votes if they want to, with the proceeds being used to pay for good causes. Would this be a good scheme?

Always start with defining the scope of your answer. In this question you need to define the terms "good causes" and "good scheme" before you can give a logical answer. You should spend five minutes planning, starting with definitions and proposed arguments. Your introduction needs to explain concisely what these definitions are and the direction of your argument. Think of it as a brief summary, it will keep you focused throughout.When you devise a counter argument, make sure to explain why it is not valid compared to the arguments you have made in support of your view. Let's assume you've used social welfare as your measure of goodness. If you have argued that the scheme has the potential to be good because it improves social welfare through donations to good causes, you should also address the potential for corruption. Corruption would reduce social welfare if the funds were embezzled for other purposes and so you need to explain why, on net, this is not as big a concern and still, overall, the scheme would be good.