Koek Krummels ...
I don’t know if you’ve made your cake yet, but you can use any type of cake, as long as you support your cake with at least 4 sticks (I use cake pop sticks or kebab wooden sticks) The next important tip is to make sure that your second tier cake is on a proper cake board. If it is too thin, it will not work, it needs to be hard. Basically, the second tier will rest on the sticks and not the cake. Last tip, make sure you glue (I use egg whites) your second tier cake board to your bottom tier to avoid it from sliding off. Be very sure before you put down the cake as once it sticks to the bottom tier, you can’t move it as it will lift off the fondant from the bottom tier.
Obviously, this only works with fondant covered cakes. Icing needs no egg whites to glue.