My pet theory is Gavin is working for Alaric probably in exchange for a major role in the Ilklan Star League . If he were working to protect the Suns he would have been more proactive in curtailing Eric especially considering he controls Eric`s closest companion giving him a complete look into his inner council. But by playing Eric and Julian against each other he can slow down reconstruction efforts and cause discord and possible conflict ,weakening a potential adversary for the Ilklan . Steiner is a dumpster fire , Marik is still trying to get there legs under them as unified nation again .So that leaves Liao and Kurita as the 2 biggest threats to Alaric`s ambitions . as long as The Suns rebuilding is a long process they can be safely ignored for later or possibly invited to join if another Civil War kicks off with an offer of aid . And with Dominion Divided Yori will have her hands full for a bit . I`m Seeing a Daoshen v Alaric slugfest in the future with everyone else busy with there own issues .
except that we see Gavin's internal monologue is he wants to strengthen the fedsuns.
I've got a few theories...
1: Gavin, much like his great aunt belives the nation will be better off under him, and he'll destroy the nation to ensure he gets the nation if nesscary, Julian and Erik are his greatest compeition so he'll set them against each other in the hopes they destroy each other.
2: Gavin isn't intreasted in Julian job but wants ERIKS job. The position of Prince's Champion has a LOT of power to it, a lot of unoffical "soft power" too. anyone who wants to impliment an agenda in the fedsuns would be VERY well served by having said position. If we simply accept Gavin's words without any catches etc and he genuinly wants whats best for the fedsuns, he may wish that position for himself, and desire to accelerate Erik's fall from grace (because it's coming)
3: Gavin is hoping by manipulating an inevitable conflict he can ensure that it doesn't blow up. and instead simply is kept at a simmer through Julian's reign.