History Anglo Spanish relations.Watch
Not sure whether this is a GCSE Q or an A level Q but if I were you I would divide my answer into three factors; domestic politics; , international politics;Elizabeths involvement in the Dutch Revolt and towards the end the English challenge to Spanish supremacy in the new world and personalities. If you wanted to do four factors you could potentially divide personalities into 'minor' personalities e.g. the Earl of Leicester and advisors of Elizabeth and 'major' personalities, thus Philip II and Elizabeth themselves.
Hopefully this is of some help but don't hesitate to ask any questions if needed.