The easiest way to split this question is by factor: economic/material gain, religious devotion, legal reasons, social reasons. In terms of historians, the more outdated view was that economic reasons were more important but the modern viewpoint is that people joined for religious reasons. You can choose which ever factor you want as the most important as your essay though.
This is obviously a very cut down and brief summary so your actual essay should include more detail and analysis as well as understanding of the topic. I would recommend organising a tutorial to go over this essay so I can explain points in more detail for better understanding!
Summary of key points to include:
(Modern view – Asbridge)
. Riley-Smith and Bull à evidence from the Charters – people sold everything.
. Raymond sold everything and took his whole family
. Appeal of Jerusalem e.g. Jesus and Holy Sepulchre
. Godfrey of Bouillon took monks with him
. Bertrand of Moncontour gave up monastic lands he illegally owned so his soul was pure
. Feudal system à chain reaction after nobility joined e.g. Count Raymond of Toulouse was the first Prince to join at Clermont.
. Violence of knights à was permitted on crusade, desirable.
. Family history of pilgrimageà Count Robert II of Flanders’ dad had developed links with Alexios I on pilgrimage in 1089 and Rob felt he should carry that on
To escape legal proceedings in the West e.g. interest on debts was cancelled.
. Count Hugh of Vermandois was the King of France’s (Philip I) brother who had fallen out with the Pope (committed adultery) so Hugh went to show the Kings willing
. Duke Robert of Normandy was the brother of William II of England who wanted to see him go and so raised a special tax in England to allow this.
. Personal advancement à Bohemond of Taranto was a second son and had failed to gain lands in the Balkan invasion with his father in the 1080s. He left crusade at Antioch. “Stand fast all together, trusting in Christ and the victory of the cross because today, please God, you will all gain much booty.”
. Soldiers received a wage à could collect booty “But not to excess” (Pope)
. Drought and poor harvest (1090s) à nothing to lose. Pope: “land of milk and honey.”
Evidence it was not actually material gain:
Raymond of Toulouse was one of the richest secular Lords in France and a first born son
. Philips: Cost 4 x a knights annual income to go on crusade
. Plunder belonged to Lords of which there where 200 out of 50-100 thousand crusaders