Im an artist. I want to post my own Nsfw art+promote myself that i have commisions.
I've read the rules and didn't quite understand that.

Can i post a separate picture of my price? Or can i link under my NSFW pieces to my FA price list? Thanks

You can not post price sheets. E621 is for archiving art, not for promotion. But you can add a link to your prices, or add the prices directly in the description. You can also add a small Patreon, Ko-fi, etc. link on the image itself, as long as it is not too intrusive. If it is just a commission, without promotion, feel free to upload it, as long as it doesn't break the guidelines.

That's a reasonable question. You can promote your work here to a certain degree, but as Dubs says, e621 isn't meant for it. What you can do is relatively limited compared to your own galleries.

Promoting anything is best saved for the description of your upload, whether directly or through a link to the price sheet on your FA gallery. Price sheets, YCH templates, and anything else flat-out heavily promoting stuff in the picture directly uploaded here will be rejected as advertisements. An uploaded picture with an unobtrusive Patreon or other promotional link should be able to stand on its own artistically to be able to stay. If the in-picture link can be hypothetically omitted and the picture's context doesn't change significantly, it won't count as an ad. Commissioned pictures likely wouldn't be advertising stuff, so would be just like any other non-ad picture uploaded here.