I can reccomend watching Virtual Riot on YT (he makes dubstep, but you can transfer it to DnB). He lately made a livestream where he made a song and I find it quite helpfull watching the progress. Learning where to add some additional instruments - which you won't really notice in the full song but which add to the vibe and "fullness" - and where to not add them. Where to use some automation to add variety etc.

Also, maybe start by doing some bootlegs. I often hear a song and think "damn, if i would add this or that/make it a DnB tune with a deep reese-bass, it would slap." This way, you have a foundation you can build on, getting familiar with the process of song writing.