I can give you advice firsthand. Went from 12 monthly listeners to over 20k, got on Spotify official playlists, and had decent money coming in every month. No manager, label, assistants, etc it was all me.
I never liked any of the playlist "services" and think they're all junk.
First thing needed is a good and worthy song. Needs to compete with what else is out there and be well written and recorded.
Make sure you submit to Spotify playlists directly with the Spotify for Artists tool. I think they say to do it 4 weeks out from release but I found it was better for me when I did it 6-8 weeks out. I also found the email for the head of rock music at Spotify at the time and I would email her directly about the songs when before and when they were released. If they were put on a Spotify official playlist, I would make sure to thank her and even make social media posts about being on the playlists.
The Spotify playlists are now largely algorithmic and a lot less personally curated. This is at least true after the head of rock at Spotify stepped down. So you need to feed Spotify information about your track using the playlist submission on the Spotify for Artists tool. Make sure you're putting tags that actually describe your song and you're giving them accurate information.
My band didn't start off with Spotify Editorial playlists on release day at first. Eventually we got there. But we had to trigger the algorithm first in order to get traction. Having people presave your song is huge and will help with that. Incentivize them to do so if needed, hold a contest. Also getting followers on Spotify will be very beneficial. Most people don't take the time to follow on there. The next thing that will help a lot is being added to other users playlists and getting streams, which is sorta obvious. But how to get that to happen isn't as obvious.
I was finding and contacting playlist curators big and small and I was RELENTLESS. I was using Facebook and LinkedIn and IG to find them and get in contact. Another trick is go to Spotify and search whatever genre or lifestlye playlist you wanna be on ("rock" "gym workout" etc.) and then type in @gmail.com, or @yahoo.com, or whatever email provider and it will show you playlists that have the curators email in the bio. They want you to contact them for submissions.
Now that brings us to money and payola. Yes, Spotify frowns about paying to be on playlists but they do nothing to enforce or stop it. I'm talking about non Spotify official playlists. Spotify "doesn't take payment" to be on their official playlists but labels are in bed with Spotify and while they aren't paying Spotify directly to be on playlists, they pay in other ways.
I can tell you firsthand that big bands, labels, and managers are directly paying playlist curators (non Spotify official) to be on there playlists. Curators have told me this directly and I completely believe it. It's a form of advertising and marketing and in the end it benefits the artist and label.
I reached out to a lot of the big playlists and they all sent me prices. They aren't giving a physical product, so it's easy to make deals with them. They'll usually let you get a trial month at a discounted rate. One playlist forgot to take us off their trial and just had us on the playlist for free for months. You can usually talk them down on the monthly price. Also looked for additional sources of funding. I visited
free spins no deposit poland several times to see new items. This gave me some money and I invested it in promotion. Most will give you a discount if you pay for a few months at a time, and will give you a discount if you do multiple songs at a time. Most will give you a good rate if you say "this playlist has more followers than yours and is charging me less". It's definitely a good idea to get trials of these playlists to see which ones are worth it and working for you and your songs. Not every song will be a good match on every playlist, but these curators dont really care and only want money.
A good portion of the followers on these large playlists may or may not be botted. I have no way to prove they are or aren't, I only see the data presented to me from Spotify about my songs. But regardless, they gave me streams, followers, and unique monthly listeners. Some people were adding us to their own playlists because they found us there. I can't help if some of them are bots. I could pay to have bots go give 1000 plays to some random bands songs and it's not their fault. But botting your songs is usually pretty obvious.
As I mentioned briefly before, I reached out to small playlists as well. Most of them aren't worth paying, so they really just gotta dig the song. It may not even be worth trying to track the person down if the playlist is too small.
But all of these things triggered us to Spotify's algorithm. We were put on "Radio" stations of other similar bands and were put on people's algorithmically personalized playlists on songs they might like because Spotify had enough data on our songs and who listened to them and what else they liked. After that, the songs literally worked themselves. To this day I'm still making money off these songs because the algorithm is still pushing them to people. Spotify took notice and eventually added some songs so editorial playlists after release.
To sum up another one of my Synner.com novels, you gotta make sure you have a high quality product and you gotta work as your own record label to push it. Don't be afraid to pay, but make sure they're worth paying.