If we sell avon or something similar can we post here in subeta? If so can we post facebook links?

There is nothing specifically against the rules, but before you do anything, you should review these two rules.

Do Not Send Advertisements Do Not Attempt To Buy/Sell/Trade Onsite Content for Offsite Goods/Currency

After that, you might consider submitting a ticket and asking staff directly for approval of anything you plan on doing. Likely anything you post in your profile would be fine. As would making a billboard ad. Making a forum topic might be okay, might be a problem, depending on how you word it and where you post it. But its always best to ask staff directly since they will make any determination of rule breaking or not.