Quoting Mother of One plus One:" I found a marshmellow recipe and a butter cream recipe. I've never had fondant,and I'm just using it ... [snip!] ... thin it wouldn't be as bad. I read the reviews on the premade and they all said it was horrible and homemade is the best"
I don't think marshmallow fondant tastes bad, it's just REALLY sweet. So I would find a really good buttercream that's not too sweet to do the icing layer with. When I do my cakes I roll the fondant out to about 1/8" That way it's not too over-powering. Fondant makes cakes look so fun and cute. It is still too sweet for my mom when she eats one of my cakes, but she just peels the fondant off. Also, add some fresh lemon juice to the fondant. It helps to cut the sweetness a little.