Android & iOS App Build

I need a complete mobile application built from the ground up for both Android and iOS. The core idea and feature set are defined on my side; I now want a developer (or small team) who can translate that vision into a polished, App Store–ready product... (Budget: $250 - $750 NZD, Jobs: Android, Appcelerator Titanium, Flutter, iOS Development, iPhone, Kotlin, Mobile App Development, React Native)