Giving material things has the purpose to learn letting go, to give up what one assumes to be his own. It's actually not an easy training and very less are really able to give. People usually give like trade, sometimes even a hug farmer joyful feeds his pigs. Neither he nor the pigs have much merits and gains in this way.
When ever you come in a situation "he/she does not have, I have" than just think of "why do I not give" if you don't do it automatically yet.
Even a short delay, listening to the defilements and you have lost:
Verse 116: One should make haste in doing good deeds; one should restrain one's mind from evil; for the mind of one who is slow in doing good tends to take delight in doing evil.
The Story of Culekasataka
It's not good to train this training for certain wordily low purposes: To reach this, to control that, to actually feed what is ones own again, or objected as such, which is mostly the case if you give somebody you are attached to. You are not really giving, but do for certain higher or lower gains.
A support for the mind means, release for the mind. If one really gives up something, the mind do no more hold on it. Whereas if you give something for your joy with it, it still clings on something and would be sad if that joy would be disturbed.
How ever, there are times and occasions where gifts are proper given, so that one has a line to follow and a security to do not unaware foster backyard defilements: Kaladana Sutta: Seasonable Gifts
Atma would not recommend Piya Tan in regard of such issues, since he has certain wrong views and does not understand the training of letting go yet.
A general overview of Dana you may find on the Path to Freedom and if you seek for more "technical" explaining Abhidhamma in Daily Life, by Ashin Janakanbhivamsa [pdf] (or online, switch language) is recommended. How ever, the best way to find out and learn is always doing by one self and by doing it, looking what's going on in oneself, what are the hindrances, what are the results. Is a practice that needs certain mindfulness and wisdom and to maintain and develop such. There are really less people, especially in modern world, who can be even called slaves of Dana (doing it for the great joy by giving), not to speak of people who are masters of Dana, may they have trained (or thought that they do) meditation for many many years, most have not even started to work on the gross defilement, so greedy are they. Yet stinginess is an obstacle fo even reach any Jhanic state...
Here is one useful talk: Sensitivity through generosity. It's not out of reason that the Buddha tells: association with people of right view, joy in giving, hostility, sharing merits... is the foundation for success to gain right view for oneself, yet it requires much sacrify to even come in contact with such people, stay with them.
(Note: this answer has not been given with the agreement to be means of trade or the purpose of/for trade and/or keep people trapped and bound. How you handle it lies in your sphere, but does not excuse the deed here either.)