Thanks @shayanmhtb, this is a great question. I’d love to see others chime in on this as it can be very broad in determining what service you want to provide and what your niche is.
Here is a guide, our DevRel director, @drew.harris put together—Building a Fintech App: A Step-by-Step Guide
Also depeneding on where you are located or country you are doing business in, can vary and determine the type of fintech you may want to create based on the locally preferred payment methods.