While a box cake mix and canned frosting is a great place to start, a homemade cake and frosting offers much more flexibility for taste and appearance. I am by no means a baking expert but it would be inappropriate to post cakes without something resembling a recipe, so here are a few things I've learned from the cakes I've made.
The Cake
Recipes
For the cake base, I almost always use this chocolate cake recipe from add a pinch.
Another recipe I like is this apple cider donut cake from cake by courtney.
I've tried other recipes, but most have been very dry in comparison.
Shaping
To flatten the cake, I cut off the rounded dome with a cake leveler or knife. It is also possible to flatten the cake by pressing down on the dome while it is warm, but I find that this creates a dense layer that harms the texture of the cake.
The Frosting
There are about a million different kinds of frosting, and I have only tried a few.
American Buttercream is one of the easiest frostings to make, but my family tends to find that a plain or vanilla buttercream it is too sweet to be used for frosting the whole cake, although it can be useful for decorating. A chocolate buttercream is much better, but it can't be easily dyed to a desired color. Cream cheese frosting is also a great option.
Decorating
I always do decoration with frosting. I never use fondant. If I wanted the cake to look perfect, I would make it out of modeling clay or plastic.
Most of my decoration is done using stencils. See my guide on cake stenciling here for an in-depth walkthrough.