Well there's no chance in fuck you have bought all of the services in the marketplace. And most of the services in the marketplace aren't that great in the first place. In fact most are garbage. So you might just keep buying garbage links if you don't know what you're doing.
There is no way anyone will be able to tell you exactly how to move your site unless you reveal it, which you shouldn't. I would do an audit of your current link profile to see what you have and what you don't have. Then, look at the sites at the top of the first page. What do their link profiles look like? What do they have that you are missing? Also look at the content and onpage optimization of your site and the top sites. What's different between the two? In general, a strategy of "match, then exceed" in terms of both content and linkage will get you ranked.
One of the most common mistakes I see noobs making is buying any PBN links and thinking that they're good. They're not. Most of the PBN services in the marketplace are total trash. If you have those trash links and a bunch of other weak ones, you won't rank. You need strong links. You also need to send tier 2 links to your tier 1 links in a lot of cases. So if you have just been buying package after package for your money site without sending any links to the packages themselves, you might not rank.
Overall there is a lot that you could be doing wrong. Your keyword might not even really be low-medium competition. It's impossible to say. Keep going and trying things and you will rank eventually. If you're using blackhat services, I would look into building your own small PBN with expired domains. You could also pay for one with a service like the one from reallife or pbn.rocks. But don't throw money at the marketplace aimlessly because that won't work.
