I don’t know what language/framework/technology you’re intending to use in your new project, so YMMV, but my experience taught me that the best moment to do event-sourcing is right from the start. It may seem overwhelming at first, but the fact is migrating an existing application to event-sourcing after the fact is somehow tedious and painful.
If you’re in the scala/java/akka world, you’re blessed : akka-persistence will do (almost all) the job for you, and I think someone familiar with akka can skim through the docs and become productive with akka-persistence in a few hours (there’s also a port of Akka in .NET, but I don’t know how complete it is).
The good thing there is that you can start with a simple storage backend for your journal (eg local disk) and later switch to a full fledged database (eg eventstore) without changing your business code (but you’ll of course have to move your data from local disk to database).
So my (humble) advice is : if you’re willing to do (CQRS+) event-sourcing, just go ahead and do it from the start, it will be extremely rewarding in the long run, and you may even find it to speed up your development.