From my opinion and experience, Treasure Tool Rope is definitely one of the most preferred types out of the four due to its ability to increase Life and increase "Critical Hit Damage". Now this is not to say that the other Treasure Tools are not good. Depending on the types of ninjas you use and what stats you want to focus on, other Treasure Tools may be as good or excels in tasks the Rope cannot. The countless players I have talked to feel that the Tools that works well for most builds is 3 ropes for your lineup ninjas and 1 gourd for your main. Gourd is great for main for its stats in Control, Defense, Life, and Resistance; a great way to improve your Main's survivability.

As you progress and you get more and more Treasure Tools, there will come to a point where you have them accessible and can really gear it towards the lineup you want to use.

TLDR: My personal opinion and the great go to in the beginning is: 3 Ropes and 1 Gourd (for main)

~Jib