The battle of Plassey proved to be of immense significance. It established British mastery over Bengal. Now it become the starting mark for the starting of british empire in India. It boosted British prestige both in India and back in Britain and raised them to status of major contender of power in India.
After battle of Plassey, East India company got diwani rights. The rich revenues of Bengal enabled company to organise large army and could meet the cost of conquest of rest of India. Mir jafar was seated at the throne who was puppet in the hands of EIC. The EIC also came to know after the war that there is no unity among Indians and it is easy to divide them
Battle of Buxar is more significant than Plassey. In this battle three major Indians power had been defeated. After this influence of company reached upto Avadh. In a way we can say that Buxar confirmed the decision of Plassey. Now Delhi the centre for political events for the last 1000 years was under the control of Britishers. It was easy for now EIC to make way for British empire.