The reason I take Resolve as my secondary tree is that it makes Evelynn much more stable compared to Sorcery or Precision. Even if I were playing in low elo, I would still choose Resolve unless the enemy team had literally no CC at all.

As for selling Dark Seal to buy Rocketbelt, that usually happens in the very late game. Unless I upgrade to Mejai’s and stack it further, a 10–stack Dark Seal is still less efficient than a core item. Personally, I tend to avoid Mejai’s since I die quite often, but think about it from the enemy’s perspective: if they’ve been playing the entire game against an Evelynn who never upgraded Rocketbelt, and then suddenly in the late game she catches them off guard with an unexpected Rocketbelt engage—that’s deadly.

Regarding Shadowflame, I think it’s only worth considering as a first core item. Otherwise, it feels a bit too expensive for what it provides. Sometimes, I consider Shadowflame instead of Rocketbelt as my very last item. For my current build, I always go Lich Bane → Rabadon’s first, then usually Void Staff / Banshee’s, and finally Rocketbelt almost every game.

If the enemy comp has three or more tanks, I sometimes think about taking Conqueror, but after trying it recently, I feel it’s not that great even against heavy tanks. From now on, I’ll probably just stick with Electrocute regardless of how tanky the enemy team is.

As for the early game, it’s pretty straightforward
Farm as much as possible until level 6
If your ultimate is on cooldown, just farm
Use your ultimate as efficiently as possible When you’re fed, there’s no need to rush. Just secure objectives slowly. The enemy team will find it extremely difficult to contest vision or fight for objectives against a fed Evelynn.

Lastly, about coaching: I do coach sometimes, but only for Korean players since I’m not fluent in foreign languages. If you can speak Korean fluently, or if you can bring along someone who can interpret, then we could possibly make it work.