Good tips indeed. I can add:

• persistence, persistence, persistence
• when commenting on other posts, please add value, since adding value is what it is all about IMHO
• indeed post on interesting topics (like this one here) BUT also try new topics! I like science a lot and recently found out SteemStem is helping science posts. Any topic you like can get an interesting follow base, but you have to find your users. Use Search to identify who post on the topic of your interests and start interacting with them! In addition I like electronic music a lot and am finding my ways to those on Steemit who do as well. I even setup a Doscord channel for a small inner circle at the moment, but I plan to come out with a project around music on Steemit sometime this summer
• promote posts in Steemit.chat and on Discord servers and if you are ok with other channels like Facebook and Twitter, use that as well (FB has some Steemit specific groups)
• put the effort in! it can take time, but time well in the end be rewarded when combined with persistence, creativity and quality
• be creative (read more here)
• support the community like you did with your post and like this post here