Rather than a revision timetable, however relaxed or realistic it may be, I found it much easier to make a grid with all the different topics in. For example for biology I had individual sections such as nerve synapses, genetic diseases, heart part names etc. I had 5 boxes after each topic, and blocked off some of the boxes in topics that I felt comfortable, for example if you have memorised the different nutrients plants need to grow and their individual functions, you may only need 2 more sessions. Once you have spent around 20 mins on a topic, scribble out one of its boxes and take a short break. Then have a look and see which topics have a lot of boxes that need filling, and work on those. Have them on your bedroom wall, trust me you will feel much better seeing how many 20 minute sessions you have put into the different subjects when it comes closer to the real exams and you feel as though you have gotten nowhere (everyone feels that way at some point haha).
As it is still quite early in the year, how about you make it your goal to try out as many different revision techniques as you can? Have a go at everything, for different topics, and when it comes to the next time you have tests, see which topics you knew the best and decide from that how to revise further.