When my boy was learning to jump he did a small amount of jumping twice a week. He was 4 at the time, so he was only doing small amounts of everything!
Usually try and have a proper jump schooling session (working on lines/turns/combinations/grids) at least once or twice a week, might have a cheeky pop over a couple of small fences for fun at the end of a flatwork session if they're up in the school on top of that. But this is on a youngster who was quite bored of being just schooled (very little jumping/hacking/cantering) in his last home, so we try and keep his work as varied and interesting as possible. He's a green 6yo
How old is he and how much work is he doing? It would depend entirely on his routine for me but if he is in regular work and not a youngster, maybe doing a mix of flat and hacking I would be doing some sort of pole/jump work two or three times a week. Proably one of those poles or raised poles, mix it up so he doesn't become bored, don't over face and be prepared to drop back a level in training if things aren't going well. Also if he's enjoying it and it's going well, maybe a visit to a XC course to pop a few small ones will encourage him X
Totally depends of the level of 'green', age of horse and the horses aim, mine are all rounders and even adult horses I barely compete jumping over 2'6. . I jump my youngster (6, been broken 9 months now) between once a week and once a month. My old dumb blood (aged 4-6) needed a few days in a row to consolidate anything and make progress. I imagine if you're aiming to event/jump the process might be a bit different. My young one is only just starting to jump 'full height' rather than crosses finishing with a straight, but again I expect this varies.