Are we talking about hand sewing or machine sewing? I'll answer for each one.
Where do you buy your sewing thread?
I usually buy my thread through whomever I may be making other purchases to save on shipping.
Machine thread was was through Zack White Leather.
Hand sewing thread was Amazon.
Which brands do you prefer?
Hand sewing Ritza 25 Tiger thread
How much or bobbins of thread do you typically use for your projects (monthly or per project)?
It really depends on the thread size.
Machine thread I can use two bobbins in a day of 207. Much less of 69 thread.
Hand sewing I use much less because I don't do much hand sewing anymore.
How many different colors do you usually work with or have in your shop?
Generally I will use Black, Brown, and White. If there's a special request I'll use any other color, at an up charge.
What’s the typical price range you pay for your threads?
Around $30 US for 16oz of bonded nylon 277.
Around $10 for 50 meters of Ritza 0.6mm
What type of thread do you prefer (polyester, nylon, bonded, waxed etc.) and why?
Bonded nylon