I wouldn't try to actually learn Quenya unless you're really good at linguistics and don't mind putting in the time. I think it's a waste of time because it's not a language that you'll ever use, not to mention the fact that the language is incomplete and there's not enough vocabulary for you to express everything you would want to say.
But one easy, fun thing you can do is learn to write English using the Tengwar (elvish) writing system, which consists of the tengwa (consonant) markings with the simple vowel markings above and below them.
I recommend the
Tengwar Textbook which you can download for free
here in PDF format.
It's fun writing English using the Tengwar writing system because you can keep a journal that no one else can read, except someone else who can read tengwar. There are several modes for English; I use the Common Mode, but once you know one mode you can learn the others very easily, there's not much difference.