I haven't actually made a 2 tier cake before using fondant so I was hoping for a little bit of help. I was planning on making a chocolate cake with fondant for my sons second birthday, firstly, is chocolate cake too soft to make a 2 tier cake with? How do I sit it on top so it does not fall in? Also, what is the best way to get the fondant figures to stick if water does not stick?

i found chocolate cakes to be very good for stacking (of course it depends on the recipe, I use either mud cake or Nigella's Devil's Food cake).  Fondant the tiers separately.  Insert 3 or 4 dowels into the bottom tier.  Apply a bit of frosting in the middle of the bottom tier and then place the top one on it.  The fondant figures will be ok to be glued with water (only a little of it though) however, cake making shops have sugar glue, which i use without fail. :)

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The support structure you put in the cake holds up the second tier, not the cake itself. Dowels or bubble tea straws inserted not the cake. a cake board under the top tier rests on the supports to keep it from falling through.

If you're having trouble sticking heavy things on, try melted candy melts or make a sugar glue by mixing gumpaste and water or tylose powder and water.