The most reliable international agency to donate money for Palestinians is the United Nations. The UNRWA is the United Nations Relief and Works Agency created to specifically help palestine refugees. You can donate to them online - https://donate.unrwa.org/
Since the Palestinians are facing starvation in Gaza the UNRWA funds are obviously being prioritised to prevent starvation deaths. The donation page even specifically highlights this: "Give now and provide vital food and cash assistance to thousands of families in dire need."
With more than 1.7 million Palestinians displaced, many of them multiple times, the need for food and non-food items is a weight shouldered by UNRWA, the backbone of the humanitarian operation in the Gaza Strip. Many rely on the Agency’s food aid for their survival. With the risk of famine increasing with every passing day of hostilities, continued access restrictions threaten millions of lives. “They have nothing in their tents. The warehouses are largely emptied of aid,” confirms Mahmoud.
... the UNRWA Supply Department has been able to provide a varied food basket containing milk and nutritional supplements for children,” Mahmoud notes. The food parcels also include lentils, rice, various canned goods, sweets, and dates. “These are the food items remaining in our stores. They are repackaged as a food parcel and distributed to approximately 8,500 displaced families inside the Tal al-Sultan shelter centre in Rafah,” he said. To date, some 374,800 families have been assisted by UNRWA food distribution, with approximately 164,082 of them receiving two rounds of flour distributions.
Source: #UNRWAWorks. Frontline heroes: The Race Against the Clock to Avert Famine
Due to the international mandate they have from the UN to protect Palestinians, they have been very active in Gaza for a long time now to alleviate their suffering:
The Gaza Strip has a population of approximately 2.1 million people, including some 1.7 million Palestine Refugees. For at least the last decade and a half, the socioeconomic situation in Gaza has been in steady decline. A blockade on land, air and sea was imposed by Israel following the Hamas takeover of the Gaza Strip in 2007. There are now very few options left for the people of Gaza, who have been living under collective punishment as a result of the blockade that continues to have a devastating effect as people’s movement to and from the Gaza Strip, as well as access to markets, remains severely restricted.
... Food security in Gaza has deteriorated with 63 per cent of people in the Gaza Strip being food insecure and dependent on international assistance ... With 81.5 per cent of the population living in poverty, an overall unemployment rate of 46.6 per cent (48.1 per cent for Palestine Refugees living in the camps) at the end of the third quarter of 2022 and an unemployment rate of 62.3 per cent among youth (15-29 years, refugees and non-refugees), the already fragile humanitarian situation in Gaza threatens to deteriorate further ... Clean water is unavailable for 95 per cent of the population.
Source: UNRWA - Where we work
Israel deliberately targets UNRWA workers and camps because some of them are Palestinians and so some obviously support the resistance against Israel, for which the Israeli-right prefers to call them terrorists:
152 UNRWA staff have already been killed and 145 UNRWA facilities damaged by bombardment. UNRWA is the largest humanitarian agency in Gaza and their delivery of humanitarian assistance cannot be replaced by other agencies working in Gaza. If the funding suspensions are not reversed we may see a complete collapse of the already restricted humanitarian response in Gaza.
With approximately over one million displaced Palestinians taking shelter in or around 154 UNRWA shelters, the agency and aid organisations have continued to work in near impossible circumstances to provide food, vaccinations, and freshwater. The countries suspending funds risk further depriving Palestinians in the region of essential food, water, medical assistance and supplies, education and protection.
Source: UNRWA funding cuts threaten Palestinian lives in Gaza and region, say NGOs