Affordable and convenient, top mount fridges are typically the easiest type to fit into standard size fridge cavities.
Available in sizes ranging from around 200L up to about 500L, top freezer fridges can hold plenty of food for your family, and even if they don't generally offer a large amount of freezer space, the freezer on top is right at eye level and easy to access.
In a household of 1-2 people, a fridge of 200-380L should suffice. For 3-4 people, 350-530L may be required. A household of more than 5 people would need more than 440L of fridge/freezer space.
Bear in mind that the larger the fridge, the more energy it will use. And as with any major appliance purchase, make sure you measure your kitchen thoroughly before making a decision.