By making an individual donation, you can have a huge impact on a public good.
Contributions of 1 DAI can sometimes mean up to 400 DAI in matching.
Your contributions will be met by matching funding, widening the reach of your donation. If 10 persons contribute 1DAI each (= 1 USD) the QF matching will be higher than if only 1 person is contributing 10DAI or 2 persons 5DAI each.
TL;DR; - Your contribution is your vote, and it's more valuable than you think. Your money is having a real impact on Gitcoin Grants.