Now normally I don't like the idea of using 3rd party but I'm currently playing a Kineticist in Giant Slayer, alongside an Arcanist, Alchemist and Warpriest . As we go on I notice a serious lack of magical item options, being a different mechanic they don't work with a a lot of the options other classes have and they have little support.
These are the options a well known Pathfinder 3rd party writer recommends, N.Jolly (possibly designed) and was wondering if they would be good additions as potential magic items?
Spheres of Power can be balanced, if you use it in flavourful ways, but can be very broken if you power-game it. The best, most balanced Kineticist 3rd party options are from Kineticists of Porphyra, as mentioned in N. Jolly's guide.
I'm not a good judge of 3rd party items balance because as a DM, I'm often willing to give all kinds of crazy items to my party, and if they're too beefy I just up the encounter strength.
The Kineticist of Porphyra rules are organized into "Other Options" alongside a bunch of other non-Spheres stuff, the wiki hasn't been just for Spheres content in a long time.
Avoid the items that give an outright DPR boost, the rest are fine. The Kineticist is already designed to do good damage without magic item support, so stuff like the Ring of Elemental Strength has the potential to get silly once you have enough d6's to work with. On the other hand I love the Crystal of Elemental Knowledge and wish it was an official item.