This is such a methaphore question. I think most important is a little cdn dot2 oven thermometer and a few quarry tiles on the top and bottom racks of the oven. With the tiles you can make most uneven ovens very even.
I also like very much countertop full size convection microwave ovens, never baking with microwave, but the rotating table gives you great level layer cakes and the convection fan is ideal if it can be turned off. There are some smaller units nowan about 0.9 cu ft which I very much want to try for most cakes now on the new book, specially the bundt pans.