300 to 400 Steem is a respectable investment.
The way that I see is that buying into Steem allows you earn MORE STEEM, MORE QUICKLY the old fashion way, curating and posting.
People seem to follow and comment more on posts when they see your vote is worth more than $ .03.

I use the CEX.io Exchange which has been very reliable and has Fiat support. Credita Cards and Bank transfers support.