It is important to remember that Lord of the Flies is about school boys ranging in age from about 6 to 12 or 13 years old. It is harsh to apportion blame to any of them, individually. Peer pressure is very real for children - especially the pre or early teens such as Ralph, Jack and Piggy.
Ralph calls on his upbringing by his naval officer father in order to establish his leadership but the context on the island is so different from the context of his understanding that it is reasonable to expect him to make some seriously poor decisions.
Ralph lacks the ...strategic skills
and is sometimes not able to find
the right word to get their attention or galvanize them to action.
Piggy is the reason behind Ralph's decisions and, whilst Piggy has the intellect, he apparently lacks the social skills required to apply his good ideas successfully.
For all his intellectual powers, however, Piggy is basically ineffectual without Ralph. Piggy is a man of thought, not of action, and he is physically weak..
Ralph would also not have been exposed to many unsavory characters like Jack in his protected home environment and so, being able to stand up to Jack - "a wily strategist"- is difficult. His daydreaming does not help and does begin to lose his grasp:
"If faces were different when lit from above or below—what was a face?"
Ralph also shows contempt at times for Piggy's ideas
"and an airplane, and a TV set," said Ralph sourly, "and a steam engine."
as he is focused on only one thing - rescue -, without considering all the factors and the many things affecting the boys. A good leader should be mindful of these problems.
However Ralph does take responsibility - which he accepts right through the novel - even when Jack has taken over and Ralph must therefore be 'blamed' (in part)for the fact that anarchy is the order of the day when the boys are rescued.
This will hopefully help you make a fair representation in your essay of Ralph's 'blame.' Navigate through the pages in the eNotes study guide for more.