Yeah it's a little annoying if done excessively by multiple lanes.
Your best bet is to say nothing and just pick up your clearing times and minimize the chance for your team to take your gold.
When you can't do that, or your team is just taking them as quickly as they spawn, then it's important to remain civil and nice and maybe kindly say something like "plz don't clear our jungle when there are lane minions for you. I get a ton of extra gold for clearing the jungle." Remember to just be chill and remain cool even if they flame you for bringing it up. At that point I'd just mute and focus ganks somewhere else.
Additionally, you can use your trinket and maybe another ward to safely invade the enemy jungle for a few gold as well. Just make sure all lanes are accounted for and that you can at least escape if the jungler finds you or a lane sees what you're doing and tries to collapse on you. This has the added bonus of providing your team info on where the enemy jungler might be, essentially denying them gank opportunities if people are watching the mini-map (don't forget to ping if you see the enemy).
Finally, and this is advanced so make sure you watch a video on this so you don't inadvertently screw over your own team, but sometimes there are opportunities to shove a lane for a teammate or to at least babysit it and ONLY last hit (i.e., no other dmg, except to last hit) until the lane looks like it will freeze for a teammate to return to it. Even if you can't/shouldn't last hit, you can still help stick around for some extra experience and help keep your laner safe while helping them shove faster. Junglers are often behind on levels as well as gold.
Examples of this include:
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You've just ganked for a lane and your teammate is out of mana or dead and there's no danger of you getting caught out. Shove the lane, pick up extra gold and experience and also deny the enemy some gold and exp while you're at it.
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One of your laners was just forced to go back or died, especially if the enemy proceeded to shove the lane and backed. Hold the lane for a few seconds picking up the straggling minions that would've died anyways. Only shove the lane if you're sure the enemy can't freeze it outside their tower because that just makes it harder for your laner when they get back.
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A lane on your team just got their own kill, follow up with them and get some hits on the the enemy tower and maybe take a few minions while you're at it. This could also be a good time to invade the enemy jungle near that lane (if done right away) because you know the laner can't collapse on you, and if the jungler comes and you ping, you'll probably have your own laner to back you up for a 2v1. This has the added bonus of deterring a counter gank from the enemy jungler (for example if you are healthy and your teammate is low on hp). The downside is that you reveal your position and status to the enemy so that another lane might get ganked, or they might try and invade your jungle while you're busy.
Anyways, there's lots of opportunities to make some extra gold and experience as a jungler. You just have to be aware of them and make sure you don't accidentally screw over a teammate by causing their lane to slow push or by stealing cs that they are perfectly capable of getting themselves.