Providers I use.
Main: Usenet Express
Backup: Usenet Farm
As well as a couple of old blocks from other providers I still have that I haven't used up.

Some of the Indexers I use are, NOT Scene specific:
NZB Planet, Miatrix, Tabula-Rasa, NZB Geek, NZB Finder
Some may have files others don't, which is why you would personally want at least 3 I would say.
Also some scene and P2P groups are uploading NZBS to specific Indexers meaning you have to be a member to get it.

You also need software to download the NZB file, like to torrent client, I use SABnzbd.

Now I must say, when it comes to Usenet automation is key and makes it so easy as well.
Look up NZB Hydra, Sonarr & Radarr.
It might take a bit to setup, but once you do, its pretty good.
You will find Seedboxes offer some if not all of the software I've mentioned.

Hope this helps.

Cheers,
Deeb