Besides wanting something reliable and efficient, you need to ask yourself exactly what it is that you want. Like, do you want new and are you prepared to suffer the initial depreciation, which is the most in the first year? Or, would you prepared to go pre-owned and at least suffer with less depreciation and a car that has better value retention.
Also, are you buying to trade up in the next few years, or are you buying to keep? The general rule of thumb would be to buy new if you're planning to change it every few years, and to buy pre-owned if you intend to keep it.
Others on here can maybe enlight you with additional factors.