Old Domain/"Sandbox" question

Google stated the sandbox is a myth. Many believe it isn't. I do understand sites can be penalized... I think... In any case, here's my story......


I buy my domains by looking through a website showing recently expired domains.

One of mine has been around for 7 years, I've had it for almost a year. I've put some orgininal content on it and have ranked for some no competition keywords.

I have another domain that's been around for 2 years, and I recently just put a forum on it. It has a few members (From me just asking specific people if they'd like to join).

If I google either one of their domains, I can see either website. I'm still very new and need to know how safe it would be to start linking to these websites with some force. My linking methods being articles and profiles.

I'm not adding 1000 links a day, but maybe 50-100. Is that a lot? Would anyone else do more? Any replies would be great.


PS: Is this supposed to be here, or should it be in the SEO section? I've seen a few posts like this in this part of the forum so I'm not sure... Thank you so much for your time Warriors!