Yeah I've used flash cards as well, another thing to is consider using the website Physics and Maths Tutor, they have loads of summaries on Economics topics which are very helpful.
In terms of revision guides I used the CGP one, not only is the information clearly laid out and engaging it's also quite funny when you read the end of topic jokes at the bottom of the pages aha. It certainly makes revision a bit more enjoyable. Alongside using the flash cards I often highlighted my revision guides, so in case I didn't revise for a while, as soon as I went back to it I'd get a visual memory of looking at it.
Lastly one of the main things to work on in Economics are the essay questions, see if it's possible to try out some of the 10/15/25 markers and send them to your teacher to get feedback. The more you do of those, the better you'll do over time and the structure of writing them will come naturally with practice.