for (basic) sewing- like garment/bag construction a fairly heavier weight thread may be better suited- i would choose a 30-40 wt thread- polyester is a stronger thread than cotton.
with thread the lower the number the heavier the thread- a 100 wt silk thread is very very fine- a 12 wt cotton thread is almost string-
visit the Superior Threads website....they have lots of (Thread Education) on the site- and free charts you can print off that tells you all the different types/fibers/weights/uses of threads; what to use them for, and even what needles are best for which threads....the site is a good resource when ever you have thread or needle questions.