Depending on what you are aiming for I don't believe investing money is actually a requirement. (obviously if you want to make a living you need a lot of Steem Power yourself). You would be surprised how big of a value is put on social interaction on this network. Sharing personal things tend to be something that gets appreciated, in that regard it is not easy when purely posting information around Sports.

There are plenty of accounts that do exceptionally well without having a big investment. @fullcoverbetting | @arfa | @notdavemate | @jlordc | ... just to name a few on top of my head.

It is not easy though and it is true that bigger upvotes usually require to give a bigger upvote back as I wrote about in this article

In that regard, looking at earnings in a relative way can be much more rewarding and put the behavior form bigger accounts in perspective. I will be posting my monthly relative earnings report in a couple days. I have not ran the numbers yet, but I'm sure that some of the smaller accounts got a huge SP increase last month.

Good luck !