It’s true - jumping headfirst into ‘The next big thing’ will leave you stranded in an ocean with everyone else’s failures. Honestly, start small. Get to grips with UE4 (They’re giving you some incredible tools to work with). Make a room with functioning objects. Then work on a house. Then two houses. Then a street.
If you haven’t already - check out the UE4 tutorials: http://goo.gl/aPG5ZO
They’ll whizz you off in the right direction.