To start off with, what exam board are you with?
Generally the best way I have found to approach questions which ask 'to what extent do you agree with this statement', is to make sure you show different sides of the argument and why your point of view is the best of those.
So with the statement 'the gods are by far the most interesting characters in books 5-7 of the Odyssey', you could say:
Intro - what your line of argument will be, are they the most interesting or not?
1. Arguments for them being the most interesting
2. Arguments against them being the most interesting, who else is interesting and why
3. Comparing the two and saying why one side is better than the other
Conclusion - summarise again your line of argument
This is just one of many ways you could organise the essay, you could choose instead to take three themes and discuss each of them in a separate paragraph.
More general advice - make sure to use examples throughout, and always explain the examples and how they support or go against your argument!