I love to bake and I'm sure I have far more stuff in my kitchen than what I actually need and at one time I know had way too much. I purged a huge amount of stuff from my kitchen and as a result I have found it has made baking much, much simpler.
Here is what I consider to be the basic baking essentials:
Mixing & Measuring
3 Mixing bowls - small, medium & large
Set of dry measuring cups
1 cup liquid measuring cup
2 Baking sheets
12 cup muffin pan
13" X 9" oblong cake pan
8" square baking pan
9" pie plate
Assorted cookie cutters
Other items I have that I find useful are:
2 pizza stones - I use these all the time.
Lemon zester - I rarely use this but it is nice to have when I need it.
Mini offset spatula