Posting content that the community will enjoy is the easiest way to get steem. If you use bitcoin to buy steempower your bitcoin will be locked up in the site for the next two years.

Although people say that if you have more steempower you will get more of a weighted vote for your curation, I have yet to see a sizeable difference that is the result of having a lot of steempower. That is to say less than 1000 SP. You can earn the person more money faster if you have alot of steempower, but I'm not sure how it is related to what you get paid. Ie, if it's proportional or not.

Curation (upvotes) will earn you steempower but not a huge amount. Commenting also will earn you steem and steempower and counts the same as submitting content. Hope this helps .