You don't need years of industry experience to create a killer app. What you DO need are
1. The idea
2. The ability to communicate the idea
3. The courage to share your idea to solicit and act-upon feedback from potential users/customers
You don't need to be a developer: There are plenty of great developers to whom you can outsource some/all of the development work if you wish.
You don't need to be a marketing whiz: Some simple strategies can massively improve the likelihood of getting your app noticed.
You don't need tons of cash: Most of your outlay will be in your own time and effort, and in the time and effort you require from others (e.g. developers, artists) to get your app built and modified during rapid iterations of honing your app, incorporating users' early feedback into improvements. You can use several techniques to reduce/eliminate the need to spend cash.
Here’s one of my own (fairly) recent app creation experiences:
In January 2012 I co-founded a startup with 3 other colleagues with a goal of building out some core platform offering services required by almost all game developers (e.g. authentication, licensing, scoring, achievements, etc.) Alas, we were ultimately unsuccessful in making that product work.
However, over lunch in July that year, with the US Presidential election looming, we had an idea:
Wouldn't it be fun to create an election-themed app that we could launch shortly before the election in order to test out at least some of the systems we'd built?
So we spent a couple of days white-boarding several ideas, honing down on the ideas that made us laugh the most. We chose 3 key ideas - two apps and an interactive video-based website.
All three would incorporate high-quality 3D models of the candidates: Barack Obama and Mitt Romey, in various activities. None of us were 3D artists so we outsourced the creation of the models of Obama and Romney.
The website would promote the apps and give a taste of our somewhat irreverent sense of humor: You'd choose the policies you thought were most important and depending on your choices, you'd see videos of the candidates fighting each other - the victor being the candidate most closely supporting the policies you selected. This was a blast to put together – choreographing the candidates’ moves made me feel like a martial-arts movie director :D
The first app, which took about 3 weeks to build, had either candidate performing one of three actions - boxing, dancing, walking flamboyantly, etc. We thought it was funny and quirky, but it only got downloaded a couple of hundred times a day - barely registering any interest at all in the iOS and Android app stores.
Deflated, we launched the 3rd app 3 weeks before the election: Gangnam President (https://www.youtube.com/watch?v=mi3gTWiGjDk) where we animated the candidates (and optional background dancers) dancing Gangnam Style in various locations including the Oval Office, in front of Air Force One, on the bridge of the Starship Enterprise, on the Great Wall of China, etc.
To our complete surprise, in its first day, Gangnam President was downloaded more than 50,000 times! It went on to be downloaded 1.5 million times in less than three weeks and became the #2 free iPad app of November 2012!
With no marketing, and only ~20 tweets/Facebook posts combined, Gangnam President took off with a life of its own.
Can lightning strike twice? At the end of November, we built another version of the app - Gangnam Santa. We replaced the candidates with a 3D model of Santa and replaced some of the background dancers with polar bears and penguins.
We launched the app 2 weeks before Xmas and ... it went nowhere. I think it got around 5000 total downloads over the Xmas period.
Success in trivial "fun" apps is neither guaranteed, nor is it lucrative ;) But it was enormous fun and we learned a TON about what it takes to build, launch, market, monetize and maintain apps in the app stores.
Let me know if you’d like to discuss further – I’ve a TON of hard-won experience (both technical as well as strategy) I can share with you to help you increase your odds of success :)