How do I invest in Steem ?

I read couple of guides here but I don't fully get it .
I don't understand how the Steem power keep increasing in my profile and based on what (I only know that votes that I get helps)

If I want to invest , should I buy Steem ? then deposit them as Steem powers or I should keep them as Steem ? I'm kinda confused honestly and I'm not sure of what to do.