Hi, I have just started jumping, and have been looking for exercises to. I am really basic at the moment, and am working up to jumping at canter. every time I ride though, I change the layout of my arena just to keep things interesting. I ride in a dressage arena sized flat space and have very limited resources. I have found many many interesting ideas and courses all over the internet, as well as distances, grids, and flat work exercises. Would this help? I just saw this very lonely post from a while ago, with a question I could sort of guide somewhere, even with my little experience.
these guys have heaps of different exercises. also just generally searching up 'grid exercises for horses' works
'horseandhound' have good ideas, and the FEI website also has some really helpful exercises.
i have found some on 'budget equestrian' and pintrest have heaps, helpful and unhelpful.
'horseandrideruk' is interesting as well. Hope this helps if you haven't already fixed your problem!