I concur with lutusp and also recommend learning Python first (or at least raw Ruby).

Before you start working with huge, highly opinionated framework such as RoR, you should understand how programming in general works. ifs and elses, functional programming and object oriented programming, patterns etc.

Regarding your question. You have to be very persistent - there's a huge amount of stuff to learn. Months of active study and tinkering with tutorials and small projects.

If all you want is to whip out a login page and a blog, then maybe it'd be better to use a CMS?