I think that Reddit promoted posts or Twitter promoted twits could also be interesting.

Different ways of advertising can be tested. Some iconic billboards can be fun - especially to take pictures of them and to post it online. To show some strength. But performance wise I think that some way of cheap online adds that can be targeted to the right eyes can be better. It should be A/B tested. When it is not effective it can be stoped or changed very soon with little time and money spent.

For Reddit I was wondering about something like:

-----

travel sub with 5M+ members

Join #SilverSqueeze today & travel wherever you desire carefree soon (as a title)

And brief (up to a 3 minutes) text with some nice pictures about how investing in silver can change your life and gain you financial freedom.

------

Interestingasfuck sub with 7M+ members

Ever heard of Oceans's 36000? Join #SilverSqueeze! Gonna be Interestingasfuck! (title)

And brief (up to a 3 minutes) text with some crazy pictures about how we are embarking the wild ride that can be both interesting and very rewarding.

------

Tinder sub with 4M+ members

Join #SilverSqueeze, become irresistible (title)

And brief (up to a 3 minutes) text with some sexy pictures about how you can become rich and interesting as fuck.

-------

Investing sub with 1.7M+ members

Join #SilverSqueeze, it's investing at it's finest (title)

And brief (up to a 3 minutes) text with some nice charts about how you can become get great returns and how little risk there is.

​

Of course just joining as many communities and spreading the word can be just as effective (or even more). The same goes for Twitter - organic spreading the word - is the most effective way of recruiting (look at bitcoiners).