You don't need to buy steem at all to contribute to the community. You can start by blogging everyday and posting meaningful comments that enriches the community. Buying Steem on my end was simply to support more of the project and the community. If you power up your steem like I did, then you can comment and reach a bigger audience because you have more money to give. I powered for my own reason because I believe in Steem and want to support Haejin.