Rambling Jack probably doesnt use many strings at all - He IS 79 !

And as Ray says ,its all personal prefereence , and dependant on your instrument ! My Martin D 35 likes Medium Guage (13 thou first wereas the Tanglewood pretty box likes Lights (12 thou) - I havent sorted the Cheapo 12 string out yet ! as to Brand , D'Addario work for me , but thats just MY choice .

And welcome to The Cat !