You can create your own playlist on Spotify and vocally call them on your Echo (I don't do it personally but I've heard it works as long as the playlist name does not confuse Alexa).
That is if you're ready to subscribe to Spotify Premium.
You can start a 30-day trial for Spotify Premium and play with it on your Echo.
Beyond the trial, here is a (French) tutorial to get a dirty cheap Spotify Premium account :
https://www.mrjeremy.fr/2016/09/spotify-premium-pas-cher.html(I went that way and I can confirm it works just fine)
Otherwise you can create a playlist using the free version of Spotify and play that playlist via Bluetooth on your Echo I guess.
That should work. Worth a try anyway