I would like to shed some light, if possible:
Buying HR views can improve ranking, but only temporary. Honestly, it is quite expensive way to rank videos, bacuse rankings won't stick.
It is better to focus on whole channel than individual videos. If your channel has authority, all videos get good rankings.
You should encourage your users to like, subscribe and share your videos on social networks.
If you use backlinks to rank video, make sure they are high quality and diversified. You were able to rank video by blasting 10k spam backlinks, but those days are long gone.
Above all, treat your YT channel as if it was your website/blog. You are not looking for quick cash, rather slowly building authority channel.