Como dizer "Adicionar gordura sobre certo valor" em inglês

We don´t have much wiggle room here, we need to boost our emergency fund.

Now let´s say you are traveling. Say, you are going on an interchange program. It would be advisable to consider a buffer (uma gordura/um dinheiro -ou economias- extra ) for unforeseen expenses.

Such buffer can be translate into "gordura" while speaking of an extra cash (usually) in your checking account, etc, to work as an "emergency fund".