Well, time is more of a goal for long-term supporters, like in Patreon or the premium version of Ko-fi, something that implies a regular income
But if you go for one-time donations, how about start by small expenses?
I have nothing more than the ink button avaliable by now, so I may not be the best adviser
But start by something small like the cost of a month of Internet connection.
Not too high of a start and it is a measurable goal, no?
Or calculate the cost of a meal where you live, and put as a goal the cost of a week of meals.
Or the cost of medication. Your relative is ill, let's put a goal that covers the cost of a pack of their medication.
They have to be goals that mean something to you and that people connect with. Not too high nor too low, so they feel it is reachable but that it is an achievement meet them