In general, you pick the thread size to suit the application -- which for gear is generally "as small as practical, but big enough to have suitable strength" -- and then pick a needle to suit the thread. Again, for gear, that means 'big enough to work properly, but as small as possible'. A needle that's too big will poke excessively big holes, and if way too big, have stitch formation problems. a needle that is too small will shred thread, or skip stitches. With a home machine, where sewing speeds are slow, you can often get away with a smaller needle than the thread charts indicate.
The gutterman 'sew all' thread sold in fabric stores is gutterman mara 100 (tex 30), sold by other places. a 12/80 needle will be fine, you may be able to use a 10 or 11.