I've made about 12 cakes with fondant, but I always have a problems with it...such as- The fondant doesn't cover the whole cake. Bulging when doing tiered cakes. and do I always have to use buttercream under fondant? These are just a few questions I have and I would love any help! Thanks so much!
P.S. I posted pictures of my cakes!

I have always covered my cake first with buttercream before I add fondant unless I am using a dummy. Whatever your cake looks like with the buttercream is what it will look like with fondant. Measure the height of both sides and the diameter for the cake top and add them all together to know the minimum size your fondant should be. Always go bigger to allow yourself some room.

Your fondant should be about 1/4" thick. As well, let you cake sit after you fill to let it settle so you will know what bulge you are going to have. Taking care of the bulge at this stage will eliminate the problem after you have fondanted. Your cake board under your cake should be slightly smaller than you cake so that you fondant can straight down to the bottom.

The best thing I have ever done to help myself is to buy the videos by Sharon from Sugar Shack. BUY THEM!!! You will solve ever problem you have ever had with cakes. Promise

thanks so much!