You could obviously record your dreams on any piece of paper, but how beneficial is it to keep a real journal specifically for your dreams?
Will I be fine even if I just use random papers, or should I keep a serious journal that’s 100% dedicated to my dreams? 
I think that isn’t important how your DJ looks, or whether your DJ is digital or paper… It’s important to write down everything to the last detail, because you are training yourself to enhance your awareness.
You’ll get better DR and better chance of having LD.
I write my dreams in my android phone and then later I convert sms into txt format with an app for my PC where I keep a protected file… And it’s actually very easy and fast. And I can do it from my bed very fast and easily…
Like dB_FTS said, there isn’t really any technical reason to have a DJ. Any piece of paper will do. Heck, I used to use voice recording in the very beginning, and that worked fine.
For some people, having an actual dream journal dedicated to the purpose adds to their motivation. I also think it’s kind of cool to have this book with hundreds of dreams in it, so that’s why I have a physical dream journal. I don’t use it as much as I used to. But it’s still really cool. That could be a factor.
I believe it depends on the person. The main focus is recording your dreams. But having a specific DJ that you’re familiar with and grow to love can improve the desire to remember dreams.
To be quite honest, the only dreams ever actually ‘write out’ are my lucid dreams. I do jot down some quick notes on all the dreams I have throughout the course of the night to refresh my memory in the morning though. My ‘dream journal’ looks like a bunch of sloppily scribbled down incoherent notes. However, my lucid dream journal is much, much nicer. 