Let’s try to sort out the noun/adjective endings with a simple

 (silly) sentence: first singular,

‘A friend of a friend provides (to) a friend a fine thing’ [= food,water, etc.]

 

 

Remember, genitives, like adjectives can modify any noun in the sentence (or serve as object of a preposition = out of/from); I just put it under the nominative (subject) to make a convenient graphic.

 

Now convert that to the plural: ‘Friends (masc. & fem.) of friendprovide to friends fine things (Remember ‘things’ =neuter plural)

 

 

 Don't forget 'equational' sentences (A=B);

in those, you have nominative on both sides of the equation:

'girls are strong': κόραι (εἰσιν) ἰσχυραί. Etc.

 

So, 'Friends.... are a fine party'