Do you build any GP/5 on Shy jungle?
None, Shyv isn't really the GP/5 jungle type. She needs items since her main strength is counter jungle; this means you're at a high risk of running into an enemy champ and need proper stats. If you've fallen behind and plan on only staying in your jungle, Heart of Gold may not be a bad idea.
When and where should I use GP/5 items? Sometimes they work, sometimes they don't.
GP/5 items are used mostly by supports since they get 0 cs but other roles can use them as well. Let me give several examples.
A lot of tanky junglers like Amumu, Malphite, Nautilus, Udyr, and Skarner can get away with building GP/5 items. They can do this because their clear times aren't enhanced by items, since they mostly use AoE's that only scale with AP to clear, and it's guaranteed gold. You would never want to build GP/5 on a jungler like shaco or Lee Sin probably. Any jungler that relys on auto attacks to jungle clear is a nono with GP/5
Top lane champs
can build GP/5 too but that's only when you've been countered, or have lost the lead, and need to play very passive top. When I say passive I mean you have to avoid all trades else you'll lose the lane. It's very situational when you build GP/5 items top and you really have to know when. Also, normally champs with mana go this route when they're at a disadvantage and start with philo stone; it provides sustain and gold. I only know of one champ, Shen, that can get away with building a heart of gold top.