People who start with 15 SP usually skip upvoting other's. They think that their upvote is worthless for the author. In reality the opposite is true. On steemit Only the person posting blog isn't counted as author, even a person making comment is counted as author. So if 10 people with 15 SP upvoted a valuable comment, then that comment author will earn atleast 0.10 including curation. This would greatly benefit everyone involved in it by further increasing the followers of upvoter. The person you upvoted might return the gesture and upvote your post.

My best advise for people with less sp would be to upvote people with less sp instead of going after whales. What this would do is that it will you earn more curation reward. Not just this but it will also help you get more followers and you might even end up forming or becoming a part of a new community.