The Final Fantasy XIV "Beginner's Guide to Eorzea" has been updated with information explaining 'guildleves'. The article walks both old and new players through the process of collecting local quests, materials, synthesis and discusses attributes and stats for the Guild of the Hand.
Q. What type of attributes and stats are best for crafting classes?
A. Attributes themselves have little influence over the progression of an actual act of synthesis. The higher the stats on the tool being used to craft, however, the easier it will be for the Quality value of the synthesized item to increase. Though results vary from recipe to recipe, a higher Quality value means that a synthesis attempt is more likely to produce either a high-quality item,* or a high-quantity yield.
Also, as the primary and secondary tool stats are different for each Disciple of the Hand class (see list below), it is important to focus on those associated with the class that you most wish to develop.
Read more here.