30 examples of textual evidence doesn't necessarily mean 30 long, fully-analysed quotes. In any given essay, 10-15 quotes with techniques is a good aim (or if studying a film - then around 8-10 scenes). Then the rest of the quotes don't need to be analysed completely to the extent where the analysis takes up half a paragraph of space. You simply need to fill up the bulk of the essay with whats called textual evidence, that is, small quotes that have plenty of meaning and directly relate to your argument. Textual evidence when used effectively will often bring home your argument in a powerful way.
You can also just use textual evidence to put in a powerful quote that you wanted to use but don't have a large enough word limit -or enough time - to be able to analyse it fully. Just ensure that it then doesn't seem obvious to the marker that that was your true intention; rushed responses never sound as complete and lack depth in the analysis.
So, 30 examples of textual evidence is completely achievable and by practicing how to incorporate more evidence into your essays now, you will help boost your marks in english.