Not sure if this quite qualifies for this community (after all - the ultimate frugal move would be to cancel Spotify and either just listen to the radio, or use YouTube/YouTube Music Revanced or UBlock Origin), but you can save a couple bucks a month on Spotify by buying gift cards and using those

Spotify gift cards are sold at a set number of months for a specific price, both of which are printed on the gift card, so they haven’t gotten around to reprinting or redesigning the cards with the up to date values yet, so they’re still sold in packs of 3, 6, or 12 months for $36, $72, or $144 ($12 a month), versus online where it’s sold as $14 a month ($13.99 if you want to be fussy). Which works out to 2 free months per year using gift cards

The gift cards last for 3 years (although I don’t know if they last on your account forever once redeemed), so you could theoretically buy 3 X 12 month cards for $432, then redeem them all, which saves $72, or 6 months worth of premium.

But they seem to be putting the prices up every year, so by the time they expire, a month of premium will probably be going for $16 or $17. Or $20 if they do what everyone else seems to be doing and shooting prices up disproportionate to replacement

Not much, and it basically only benefits people with enough money to actually drop 400 bucks on Spotify at once, but even buying a 3 month voucher saves about $6