We should receive a feeling of completeness in knowing that we are helping to spread the Gospel of Jesus throghout the nations as was commanded by God.
We can offer the support of Prayers, Clothes, Food, Shelter, Medicinal needs, whatever is available or at our disposable. Sometimes a kind word can do a missionary more good than any amount of money we have to give.
We must remember that not everyone believes there is a God and Missionaries come into more discouragement by words than by deeds.
As long as we remember that we are to love our neighbours as ourselves we should have no problem with giving support of any kind.