The only really successful way I've seen people grow on Steemit (especially from nothing) is organically. It requires genuinely getting involved with communities and participating to bring some kind of value to the platform. There are many communities already growing on the STEEM blockchain and future updates should empower communities to do more to facilitate their own growth and user base.

I think it's important to know what doesn't work to avoid doing that as well. Spamming links to your post on other people's posts, making spam comments that clearly indicate you aren't even aware of what the post you are commenting on is about, and throwing money at bidbots for every random thing you can do don't seem to be very effective ways to use your time on the platform. Most people actually view these things as in some way hostile and devaluing the platform and they're likely to result in flags.

TL:DR get involved with the platform because you actually enjoy using it and provide quality content or value to the platform in some way.