What type of app you suggest us to make?

[OrangeCleaner]

If you can come up with an innovative game concept idea that would be your best shot!

 

[siddigTheCat]

Since you are new to development then a small game that will not take too long would be a good starting point.
There can be a lot that goes into the development of a game such as audio, artwork and coding. So I would start
with something using free resources to help cut down the work.

Marketing your application once done (or near completion) will be a large task in itself (as I am just learning after
having published my first game).