The only time jungle shouldn't gank is if they're behind in levels/gold and have a hard time when they do gank, most junglers have a decent way into lane. I play heavy gank junglers primarily (rengar, zak, khazix, and tryndamere) tryndamere is lesser gank focused atm because of having to stack devourer but that'll be gone next patch.
with junglers i feel like they're the "Pin sitters" of the game in a sense, because if someone in a lane dies, and they're nearby they can come in, push back the wave to middle ground (cause most times someone gets a kill they either recall or are low, either way) you come into lane, reset the minions so theres no turret damage, and leave when laner comes back. although, I do not think it's the job of the jungler to come to whatever lane is pinging for help,
the jungler has the right to decide where he spends his time. I usually ignore pings and just do what im going to anyway because most lane players do not play jungle therefore don't realize the intricate details of what is involved in jungling, timing your smite for certain camp buffs, staying hidden from wards, making sure you dont get counterjungled, timing buff and camp respawns for optimal farming, scuttlecrab and drag/rift herald control, jungling is a very complicated role in iself just because it isn't as simple as being in a lane and holding your tower and farming
when a jungler stops what they're doing to help a lane pingng for help, either A-was already headed there anyway or B-left what he was doing to help.
a lot of the time if you want a gank what you'd want to do is watch where the jungler is at, example is if you're on blue side top lane, and you'd like a gank from a jungler that starts red buff, you're probbly not going to get it as soon as the game starts, because of him being on the opposite side of the map, but if you notice your jungler heading to top side jungle, you can let the minion wave push and let the enemy laner overextend, then ping for a gank. I'm more inclined to help lanes I'm near than having to go across the map ever. though if you'd like the jungler to hold lane so you can get items, only bad ones will ever not ablige, thats freefarm that the jungler would otherwise not have and that nobody would have if they would have died to tower while you are away.
Also, ryze jungle sounds like it would be good to an extent, he has a shield, a root for ganking decent wave clear when he gets ult and sustain with ult as well, (which is on a pretty short cooldown since the rework) I've never tried it but it actually sounds pretty decent as long as you can survive the first 3-4 levels, going to try it out later on tonight