Well IMO the first thing you may want to do is establishing the budget you wanna spend on your build. I don't want to scare you but along with Vader, Fett is known for being one of the more expensive SW build if you are looking for screen accuracy.
Depending on your abilities, you may decided to do some element by yourself to reduce the global cost.
When I started a year ago, I decided a 2500 € budget would be enough for my build and I managed to stick to it, but again I did a lot of thing myself. You can see the progression here
if interested. If you want to poursuit this hobby for years, be aware that you may want to buy again what you first choose for low price reason.
The cargo hold section can aslo be a good opportunity to get some second hand elements.
Personnaly, I started with the helmet. Most iconic element, and I know I would keep it even if I would have decided to not finish the build process.
Welcome to the hunt