http://wiki.project1999.com/Skill_Ta...Leveling_Guide
You'll be crafting
http://wiki.project1999.com/Silk_Swatch by combining 2
http://wiki.project1999.com/Spider_Silk which drop off of adult bonecrawlers and bonebinders (not hatchlings) in Field of Bone. That will take you to 21 Tailoring.
Alternatively, you can craft
http://wiki.project1999.com/Silk_Thread by combining 2
http://wiki.project1999.com/Spiderling_Silk which drop off of hatchling bonecrawlers and bonebinders in Field of Bone. That will take you to 15 Tailoring.