Copy your loop along the timeline so that it’s covering roughly the amount of time that a finished track in your genre would be. Then go back to bar 1 and start deleting or muting the blocks for the MIDI / audio parts on the timeline that typically wouldn’t be playing at the start of the track (like the main riff for example). Build things up gradually from just basic percussion, adding new elements every 8 or 16 bars to start with.
When it feels right, usually around the 1 minute / 33 bars mark, drop your bass in there. Let that run for 16 bars. Then, section by section, start adding your other elements bit by bit for another 32 bars or so.
During this part of the track leading up to the breakdown, I would usually advise against adding the full main riff in just yet. We don’t want to ‘spoil the surprise’ of the main drop that’s coming after the breakdown. If we added it here, the track could become samey and boring by the time we get to the drop if the main theme has been running for a while.
Saying that though, If you want to introduce a stripped back version your main riff before the breakdown, that can usually work well. A good technique would be to chop a couple of notes out of the main riff to use as stabs in the sections coming up to the break. You could try a couple of things here like maybe filtering or fading the stabs of the riff in gradually on the section leading up to the breakdown. This way, you’re starting to subtly introduce the main riff, but you’re not giving the whole game away about what’s coming next.
You could even try using those same MIDI notes that you cut out, but use a slightly lighter sound or a less layered version of the sound to the one that you will be bringing in fully after on the drop. This way, the main drop will have a lot more impact as well when it hits. Maximum impact is key here to get everyone going nuts on the dance floor, and also to make sure that the A&R people from whichever label you sent it are going to be to jumping out of their office chairs with excitement, resulting in them hopefully signing your masterpiece. These are both your goals for any track so if you get this part right, you’re onto a winner!
Now we’re up to the middle section of the track. Carve out a makeshift breakdown to use as a guide, somewhere around 32 bars long (48 bars at the very most) Now already we can see our target, which is to get out the other side of the breakdown and into to the main drop.
After a couple of rounds of the main drop, then its time to build it back down gradually to an outro where DJ’s would be mixing the next track in over the top. For now, just make this outro symmetrical to the way you built it up, something similar to the picture below.
Now like some crazy voodoo magic… we have the main core of our track all laid out.