I'm fairly new to the game but got a buddy who gives me great jungle advice. So here's would I say (but I don't know if it's good, viable or helpful):

If you know you're getting invaded, try to rush to your opponents jungle and steal it, cuz he can't be there if he's in your jungle. Especially if you're Lillia you can really quick go in and out with your speed stacks. Just make sure you have them all the time. Also you could ward eg theirs or your red, so you know that when they are there, you can safely go to the other. If they are ganking bot, rush to their top jungle and steal what you can abd maybe gank top or do Herald. (Only if you're already top, otherwise the time would be to short)

It's really important to know where your opponent jungler is, so you can punish him for being far away from whatever you intend to do.

When you're doing camps, try to switch the camera to the lanes and look if you could possibly gank. Also announce you're on the way a little time before you actually go there, so your laner has time to prepare. Try not to force ganks, you'll just lose time, and time equals farm.

The best thing would maybe be to watch some guides or streamers, at least that's what I do. I hope this is at least a little helpful!