From now on, we need to think (carefully) about where and how to prioritize (our spending)
「優先する」= prioritize
「どこをどれだけ」= where and how
「我々はこれから、どこをどれだけ優先するか、を考えなければならない」= From now on, we need to think (carefully) about where and how to prioritize (our spending)
※spendingは「お金の使い方・使い道」という意味になります。