What is a good conclusion for the influences of Hamlet?I need something good to understand it.

I think you are asking for things that have an influence
on Hamlet's behavior and attitude in the play.  If so, here are a few things to
consider.

One strong influence on Hamlet are his religious
beliefs.  He vehemently opposes the marriage of his mother and his uncle because he
regards it as incestuous, as would have the Catholic church at the time.  He also
considers suicide, but doesn't do it because it is against God's
laws.

The ghost influences Hamlet to take vengeance on
Claudius for his murder.  He makes sure to tell Hamlet exactly what happened to him and
how he feels about the marriage of his wife to his brother so that Hamlet will feel the
emotional tie to his father and do what he is told to do.  When the ghost returns in Act
3, Hamlet is influenced to stop being so harsh with his mother and focus his attention
on the task of vengeance.

Fortinbras influences Hamlet from
afar.  Hamlet sees Fortinbras going off the Poland to fight over a worthless piece of
land and Hamlet is then inspired anew to take his vengeance against Claudius -- to fight
for something that is very worthwhile and dear to
him.

Claudius influences Hamlet to do he needs to do to
save himself.  Hamlet reads Claudius's note intended for the English king, and decides
re-write the note to condemn Rosencrantz and Guildenstern.  This isn't something he
would have done in other circumstances, but Claudius kind of forces his
hand.