I use Oregon needles, which is what came with my Janome when it was new. I never change sizes for FMQ.
I can't remember offhand what size I bought, though. I never change needle size, whatever size it is that I bought seems to work fine for everything I need it to do!
I buy them by the 100 from Amazon; it costs around 12 bucks for a box of ten packs of ten needles.