It will start to have trouble around level 470 as an Abyssal.
In general, if you look at Gilas - Neon War Dragons and check what base level is needed to reach the highest level for a particular stone, that’s a reasonable indication of the base level you can take on. In this case the abyssal stone will get you to level 95, which requires 467, which means level 467 bases should be quite doable for him. Incidentally level 95 also means it’s balanced to fight level 95 towers for modern divines, so that’s another useful indicator.
Dragons tend to become stronger with seasons, so getting a dragon now for a level you won’t reach until 3+ seasons from now has somewhat limited use. I don’t know your current level, but if it’s still below 150 or so I think it’s pretty safe to assume 470 will take at least 3 seasons to reach.
Still, finishing Gilas is also not bad, the resources in the dragon line are pretty ok. I would just not open chests for it, and I would take trading post chests over finishing Gilas too. If you earn enough sigils to both get the trading post chests and still finish Gilas, all the better.
Yes I would recommend saving bronzes too, if possible. But of course you still want to grow in fort and breeding, and participate in pvp too, so it’s not an absolute rule. But anything you can save for discount week next season will give you a solid boost.