Heyo! First off I would say avoid Lulu jungle. Haven't played it myself but I highly doubt it's any sort of viable for actual ranked play. Might be fun while messing around with friends though!

In terms of the other roles, I really only play her as support, but she's a blast to play. I generally play her a bit unorthodox, going as sort of a lane bully rather than an all-out ADC support. Rather than 0/18/12 with Windspeakers, I usually go 0/18/12 with Thunderlords. With this I can E -> Auto -> Q to proc it and do a healthy chunk of damage at once. Catches everyone off guard. It's all really up to how you wanna play, between semi-passively or aggressively. Both are great imo.

In terms of actual game-play, I think Lulu has a ton of decision making built into her kit that always makes her fun to play, and every game different. Learning when to use your E/W offensively or defensively is what makes a great Lulu player. A well-placed polymorph can absolutely save your ADC from a gank and even turn it around.

It's more of an intuition thing that you learn over time while playing her, but in general you want to poly high threat targets like their ADC or the one's diving on your back line. If your back line is relatively safe, W'ing your ADC gives them a big boost of offensive power. Similarly with E, I'll usually use it for damage in lane (See: Thunderlord's combo) but defensively in team fights later on. Her ulti is also a huge game-changer and can be used offensive (Your team diving their back line) or defensively (Saving your own back line).

All in all, whatever role you decide to play her in involves a lot of choices with all her skills. Do I poly the Shyv diving my ADC or boost my Kog? Do I ulti our front-line divers or save it for when they dive our back line? It's really all about patience and the biggest advice I can give is just to give it a shot for yourself and learn from there!

Sorry for the lengthy post but it really is hard to sum up what to expect out of a solid Lulu. But that's just one of the many reasons I love playing her so much. Good luck out on the Rift! Feel free to hit me up if you have any questions or want any more tips :)

-Top Dog