I am looking for strong sutta references that say that dāna/generosity is the first element of the gradual path. Which text is/are most often cited? Thanks.
A good reference point is when we see the summary of the Buddha`s gradual teaching (anupubbi-katha):
Suppabuddhaṃ kuṭṭhiṃ ārabbha anupubbiṃ kathaṃ kathesi, seyyathidaṃ—dānakathaṃ sīlakathaṃ saggakathaṃ; kāmānaṃ ādīnavaṃ okāraṃ saṃkilesaṃ; nekkhamme ānisaṃsaṃ pakāsesi.
"(…) having regard to the leper Suppabuddha he related a gradual talk, that is to say: talk on giving, talk on virtue, talk on heaven, the danger, degradation, and defilement of sensual desires, and the advantages in renunciation—these he explained.
The key word may be dānakathaṃ.
A note is that it is not necessarily defined as first step in the path, I always thought of it as the first element of the gradual teaching.
But I think different words apply to the same thing, including for example the element of thoughts of renunciation in the right thought factor of the eightfold path.
Although like Gabriel said but still important as faithful householders to give food to the Sangha. So rather than just listening only to discourses like as if your a Hearer only, have more faith go a step more in faith by giving to the Sangha. I think there is many times Buddha mention it. But it wasn’t like propaganda. Some people never get much faith to feel to give food to the Sangha. Which brings much blessings. I think seeing it like that it’s our responsibility as Householder Citta to truly support the Sangha. Buddha said we should imitate Citta the Householder. And he gave a lot.
In my opinion it is like the whole path of a householder. Giving. Your lowering greed. You being unselfish. Giving your making a right thought. That there is worthy ones that are worthy of your offering.
You need to have a right livelihood to be able to give to the monks
Your practicing right action by giving monks
Your practicing right intention
If you invite the monks for food, you will get the chance and need to practice right speech.
When giving the food with right mindfulness.
So if I compile the examples of other householders. I think the Sangha made them into sutta was to inspire to the Path.
Just like good friendship is whole of the path. Being unselfish is whole of the path. Give @Gillian
If I find anything in Agamas for example I will private message you
Buddha said to householder the wrong view that some brahmins and sramanas had.
“If one were to go along the north bank of the Ganges giving gifts and making others give gifts, making offerings and making others make offerings, because of this there would be no merit and no outcome of merit.”
But if we have RIGHT VIEW
“Since there actually is doing, one who holds the view ‘there is doing’ has right view. Since there actually is doing, one who intends ‘there is doing’ has right intention. Since there actually is doing, one who makes the statement ‘there is doing’ has right speech. Since “there actually is doing, one who says ‘there is doing’ is not opposed to those arahants who hold the doctrine that there is doing. Since there actually is doing, one who convinces another ‘there is doing’ convinces him to accept true Dhamma;  and because he convinces another to accept true Dhamma, he does not praise himself and disparage others. Thus any corrupt conduct that he formerly had is abandoned and pure virtue is substituted. And this right view, right intention, right speech, non-opposition to noble ones, convincing another to accept true Dhamma, and avoidance of self-praise and “disparagement of others — these several wholesome states thus come into being with right view as their condition.”
The Middle Length Discourses of the Buddha
Nanamoli & Bodhi
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Since believing that giving gives merit. Then as seen above RIGHT INTENTION AND RIGHT SPEECH is also involved
So the Sangha in going almsround etc is directly letting us practice right view. The first path and others also