With your current SP level your vote is always going to be dust unless it's stacked on top of other votes. This is fine as long as you understand it and use the votes where they will matter which most of the time will be on the post.
With the free SP you are getting there is no reason to power up until you can buy more then you currently get. That power goes away on a 1 for 1 basis. So if you power up 5sp you will loose 5sp in delegation.
Watch the market, you have a good amount of SBD. If SBD becomes higher priced then Steem convert it over and then power up. I've gotten 1.1-1.15 steem per sbd multiple times. Right now it's about 0.8 steem per sbd so it's a bad time to use SBD for powering up.
That's basically what I try to do. Yeah I want to upvote all the people through pay it forward, especially the ones I nominate :D I'll get there though. I guess. I'll just save up money and wait for SBD to drop again.