Stickers and stamps can be used to encourage learners but also for the ease of your own marking.
Peer assessment can be an excellent strategy but students must be taught to do it effectively. This post explores how feedback guidelines can be used to achieve this and there are links to examples of feedback methods that you can use yourselves.
Ensure that English and maths are included in your feedback.
Target setting after feedback is important. Students can do it, or students. Here's an interesting idea from @HuntingEnglish about how students can engage with targets for improvement over time. They review all targets, note them down and traffic light colour code them as to whether they've achieved them yet.
Closing the gap is an essential part of providing feedback. On formative assessments, students should be given the chance to amend their mistakes. If they don't, it's likely that they'll make the mistakes again in the future. Can you set aside lesson time for this?