yeah, i guess i'm backwards too. i usually find a break close to the type of track i want and drop it in a channel to use as a metronome. then i skip all the drums and write the main hook/synths/bass. once the synths are close, then i go back to the drums. from there, it is a see-saw between the synths and the drums until everything sounds good, then the mixdown.
for the synths, it all boils down to two things: your ears and your skills. first, you can learn a lot by pressing buttons and turning knobs. but ultimately, the better you can learn your synthesizers, the more professional your sound. so take some time to figure out your gear, and don't go and buy/download 500 vst plugins if you can't work the first few.
drums are a bit tricky (well, sh*t, it's all tricky), but they are the easier of the two. while synths take creativity and artistic form, the drums can be programmed with a simple understanding of how DNB drums are built. this is not to say you can throw a few samples into their prescribed positions and call it a day. your drums will not sound like they fit your song unless you fit them to your song (duh) but if you follow some basic patterns, you will end up with drums that sound like dnb.
typically, i start with the previously-mentioned breakbeat. once i work out some synth noise, i will go back to that break and high-pass it. then i add one or two kick drums and 2 or three snares. i start with good samples and load them one at a time in my audio editor. i compress them, and then normalize them before putting them into my daw. this gives a nice thick sound from the start, and you don't waste processor power compressing the channels. next up is the high hats and high percussion. some single hits, some loops (homemade or commercial), whatever it takes to get things rolling. i usually end up with about 12-18 drum channels to get a nice full kit. again, use your ears.
then you need to fill your track out, this can happen two ways. adding sounds, like effects and builds, and repurposing sound, such as a kick roll. you need to have a lot of variety in the track to keep interest, so this is an important stage to f*ck with a lot of different sounds. i like to map a lot of different sounds across my midi keyboard and just let the song roll, try to hammer on the keys and find sounds that work. another good method of adding variety is to bounce down your synths/basses and cut them up and effect them. back to the ears!
then, you have to mixdown, get everything sitting right in the mix. i am no expert on this stage (or any of this, really - follow my advice at your own risk). i typically turn all of my faders to zero and bring the sounds in one at a time. get them to gel before bringing up the next fader. i'm sure you can search and find a few threads on using eq and compression and so on, so to avoid misinforming you i will leave it at that.
hope this helps...