Context: I have given around $1000 to GiveWell this year and I am considering giving around $1000 more. I'm a college student, so that works out to around 10% or 20% of last year's income.
It seems like EA-aligned causes and professional grant makers like the FTX future fund have more money than they know what to do with; the general consensus on the forum appears to be that EA is (for the moment, at least) no longer funding constrained. If this is true, the case for direct work seems very strong, but the case for personally giving seems weak.
I don't expect to do better than e.g. William MacAskill when selecting funding opportunities, and if he thinks that last-dollar funding is not cost effective, why should I? (I know that professional grant makers think that last-dollar funding is not cost effective because they aren't funding more projects, but aren't out of dollars.)
In other words, professionals I expect to be able to make better decisions then I am think that marginal EA-aligned funds are better saved than spent right now. Why not do the same for my personal giving? If the EA landscape doesn't return to being funding constrained, why ever give more?
The other people gave reasons why you might want to donate money on the margin. But my personal guess is that in most cases, college students in EA probably should not be donating large amounts (to them) of money, and instead invest it in either improving their own career capital, or (if they don't have good social or governmental safety nets) saving.
Almost all of your wealth as a college student is in human capital, so investing $s in ways that lets you either do direct work later or donate much more later is likely the best route to impact for your money.
To my eyes, honestly the strongest reason to donate money for most people in your position is something like "identity formation": you might consciously want to form an honest self-image as someone who cares about others and is willing to make large personal sacrifices to do so. I did this when I was younger, and I'm glad to have done so. But on the other hand, I value money now much less than I used to, and if I could send money back to my past self, I would gladly do so.