Choosing a filler metal is a little more complicated than selecting based on yield strength.
Here are some basic question you you need to know and understand.
What is the metal or metals to be welded?
What are the dimensions of the weldment?
What type of current is available?
What are the required positions?
What is the fit up required?
Are any specific properties of the filler metal required?
Does the weldment have to meet any code or standard? If so do
you have procedures for using this filler metal?
One could elaborate on each of the above questions and add a few more, but this would get into writing a book.
if you are going to do a lot of selections you should get a copy of ASMF Section IX. Expensive but almost a requirement for most codes and standards.
At you welding supply house there are usually have booklets or guides available for a small fee that outline the selection of fillers metals based on their products.
Here are two very good inexpensive books from Lincoln Electric that cover some of the above along with welding in general.
New Lessons in Arc Welding and Metals and How to Weld Them from Lincoln Electric.