Find a local seller - Facebook marketplace, Ebay, Ebid ← (You can sell shit here too.) and many more. The overall premise is to find a place to sell your product.
For this method we’ll be offering a Spotify account upgrading services. Simply look up “buy spotify cheap” and find a webiste you trust. Personally I’ve used g2a/z2u in the past but it’s up to you what you use. This step does require a small investment but it’s worth it if you put the effort in.
Now market on these selling sites that you’re selling Spotify premium for x amount off the original price. If you can use photoshop to create some catchy marketing material illustrating what you’re selling your sales will most likely increase.
When somebody buys your service, treat them professionally and always answer their questions. Word of mouth is extremely powerful and if you’re reliable you’ll inevitably gain traffic via your customers.
Be creative with your marketing and offer package deals etc.