As Rami mentioned, the key thing many new entrepreneurs forget (or refuse) to do is prove that someone (in numbers) will pay for you to solve their problem, make them happy or entertained, or increase their capabilities.

Many ideas are appealing to your target market but they may not see enough value in them to actually lay out cash and pay for that value. Part of building your business model is connecting value propositions to customer segments, and communicating these to your "sample" customer segments. And LISTEN HARD. If you hear a bunch of "yeah, maybe..." or "no", chances are you may have identified something with value but you are communicating the wrong value proposition. Or to the wrong customer segment.

Do not skimp on this step. Before you invest any more time in your product development or skills development, PROVE that you have customers that will pay. AND THEN, you still have work to do. You need to prove you have a business model that will work - channels for finding these customer segments, revenue streams that have the potential (realistically) to cover more than your costs (which you obviously need to have thought through as well).

Start with the Business Model Canvas and force yourself to be disciplined and honest. You may need to pivot until you have the results you want but that's WAY cheaper than trying to pivot after you have invest thousands of hours and dollars in building your "best best" product. A sketch on a napkin is enough to demonstrate the concept to potential market segments.

My final thought is don't forget about your operations. Eventually you will have to learn how to run a company. Get on top of your foundational stuff sooner than later because if you do have the billion dollar idea it's going to take off quickly and if you haven't put the building blocks in place to help you grow quickly, you may find yourself in hardship. Get a mentor who can carry you through those steps and help you plan for growth.

Let me know if I can help you further. Good luck!