First of all you need other ppl to tell you it's a billion dollar idea. Tell it friends and family, would they buy/use it? If they say "yes", ask them to "vote with cash" and give you a couple dollars as an upfront payment for hat you are going to make. The more ppl will give you money they more your idea is worth. Then try to make a minimum viable product by yourself if possible or just a demo. After that you can if it's worth you go and make your ICO or get the early stage funds from VC. You need to show ppl you've got something before you start asking for money. And even a small demo is better than nothing.
Let me know what you decided ) and how it goes