After your brainstorming ideas, don't you dare throw that tool away yet. You will need it throughout the way. However, you should take a look at your own skills and how much help you need. How are you going to achieve the goals you just set for your app, and most importantly, who can help you achieve those goals?
Behind every app, there is a code. And behind every code, there is a coder. Even though coding has become more popular these days and more people want (and are easily able) to learn it, it doesn't mean there is a coder behind every corner. But when you do find that one coder who suits your vision and ideas, lead them along and share every single idea you have. Make them know your own visions by heart.
When launching an App, you have to be familiar with App Store Optimization, if you are willing to have your app succeed. When people are scrolling through the App Store, what catches their eye? That's right - images and videos. You will need a graphic designer or someone with the right eye and photo editing skills. If your app is a game, having an animation maker is a great advantage as well. And always, make sure you lead them to YOUR own direction. Graphic designers are creative, and many could have different styles and visions. Search for the right one for you, or find someone open for YOUR ideas and YOUR ways of doing things. But also, be open to their professional view of things. If you find someone who has been a part of this creation process before, they could have essential knowledge of the field.
Now that we have mentioned ASO, you probably figured out that there is nowhere to go without marketing. A marketing expert will help you regarding ASO and on general knowledge on what has worked, what has not, and what will work for your app.
Last but not least, use your friends and family and every possible "App user" as possible, from brainstorming to the actual testing of the app. They will give you the feedback before it is for the whole world to see.
In addition to the latter, the most critical talent you can find to your team is the talent of supporting. You need a team who share the same goal and values as you. You need to be able to brainstorm together and sometimes even disagree with bringing other options to the table, but at the end of the day, have the same goal.