Hi @arthur.s0g! Steem Power is more of a long term investment in your channel and the Steemit platform. The more that you have the more influence that you have, and the more that your upvotes provide value to the user who's post you upvote. Steem back Dollars can be easily used to purchase more power, or cashed out by transferring them to an exchange (like binance or through steemconnect). Often you have to go through another coin like ether or bitcoin to withdraw to USD.

As for your posts, I would suggest posting few times, but putting more photos and content into each post. Comment on other users posts and expand your network.

Best!