My job & passion is to help mobile first-timers. Dealing with limited resources (or efficiently leveraging existing ones) is extremely common.

Building a working prototype to test the market is quite quick nowadays. The foundation of an app, especially before it is well-established should be clean UI and efficient task execution.

Considering (among other things):
- Apple likes when their native UI elements are used
- users like something they feel comfortable with upon first use
- there are many available apps you can use as a style/design reference
- you should avoid "stuffing" your app with additional features
- there is always room for UI/UX improvement but first, you need data/analytics to know what to tweak
- you mention "business plan", which makes me think the business itself might need some real validation

My advice is to hire a developer to release an MVP.