what’s the secret to really great smelling laundry?

I’m constantly coming across people who smell really great, like clean laundry, and I can’t help but wonder why my laundry doesn’t smell as good..

Any tips? I’m allergic to Tide, so I can’t use that and I dont’ have a dryer so it needs to be something that’ll hold up to line-drying..

any tips?
i’ve smelled someone who uses the gain combination and it IS good!!