I'm not a pastry chef by any means, and did poured fondant badly many times before I quit struggling and started following instructions. Pastry is picky, I feel your pain.
Did I mention picky? The key isn't high temperature, it's the right temperature range. You have less than 10 degrees to work in -- better if you could keep it within 5: 98F - 102F, inclusive.
I also know that recipe -- it's basic (rolled) fondant, and heated to the right temperature, needs some simple syrup to pour thin. I can't tell you how much because it's an eyeball thing with everything at temperature. IIRC, it will take around 1/2 to 3/4 cup.
Not to over stress a problem that hasn't happened, but you have to be careful not to overheat either. A too hot fondant will pour well, but won't glisten when it dries. As close as you can get to 100F, and lots of stirring to keep a skin from forming.
So... the big two investments: Thermometer and ladle.