Hi Joe,
Definitely get a focal reducer, getting the scope to track accurately will be easier with a shorter focal length.
Filters are not essential, starting with monochrome imaging makes life simpler. It may be worth getting a UV and IR cut filter, this will remove the UV and IR light that the scope may not do a good job of focussing.
You don't need to get adaptors to start with, you can use the T to 1.25" adaptor that the camera comes with and fit the camera instead of an eyepiece.
I would get a SCT thread to T adaptor and some T extension rings. The camera has a T thread so you can have everything screwed together. This is a bit more secure.
You didn't mention guiding. You will need to guide if you want to do longer exposures - more than 30 seconds to a minute.
Another thought, if you get a small refractor - 66mm or 80mm - this will have a shorter focal length and make collecting data easier because of the shorter focal length. Then get a guide camera and use this as a guide scope with your SCT.
But to start with I'd get nothing but a focal reducer and a UVIR filter.
Chris