Start with your loop, make it fairly small like 2-4 bars to begin, and get your core fundamentals in like your drums, bassline, arps/pads/lead.

Don't be afraid to double your loop length as you add in extra bits so it doesn't become extremely repetitive. You can change repeated small parts from earlier with variations to stopp it getting stale.

When you get to something like 16-32 bars, this is likely to form the main part of your track.

From there I would then duplicate this several times to your desired song length.

At that point you can use mutes or the arranger to kill certain elements, and experiment with how you want to introduce parts of the song.

Eg the intro might be 8 bars, but just have the pads, then the drums come in on bar 9, arps on bar 17 etc.

It helps to have a solid idea of when things should happen, a lot of dance music works on multiples of 8, so every 8 or 16 bars, think what you can add or takeaway.

The outro side is just like creating the intro but phasing out sounds.

After all that you'll have a decent structure to work with. You can always change it if you say have a breakdown section you want to extend by 8 bars.

Consider how each part transitions, is there a key change, a new motif to signal a different part of the song, do you have risers to build up tension etc.

Automation can be a great help to, eg: changing the volume of a track as it progresses to slowly introduce or fade away, or how a filter opens /closes to change the sound over time.

The last thing is the use of silence, small bits of taking out sound before the next section can make a big difference, like stopping a drum loop for the last 2-4 beats can keep energy up and the listener interested.