No one can /will teach you to design or develop for here.
Assuming you focus attention on high quality and original design, best practice structure and coding then you have a good chance of being approved.
If you are at a relatively basic level then take a decent amount of time to understand the attention to detail, quality and versatility required for approval here.
The single worst things you can do is either focus too much on earnings (it takes time) and/or rush to try and complete something.
Also read this blog A Customer's Guide to What Makes or Breaks Items