If you have a strong belief and looking for a long term here in Steemit, then having permanent SP is much better than those rent and promotion. But renting SP or promotion will works the same, you can be popular somehow that you might tends to attract more engagement and new potential followers. If you are going to promote, then make sure about its quality and try to make it into the trending page as you can, so it can be more effective. While if you have at least 500 SP or more, you can upvote just like poking even a thousand user.