Do you already have BTC? For BTC/fiat trading, some of the best ones for liquity I know are coinbase/gdax, bitfinex, Kraken, bitstamp, Gemini....but if you don't have USD or aren't able to access those because they don't serve your country, I guess you would need to find some other local exchange in order to get BTC.
Once you have BTC, then probably the main exchanges to get hold of steem are:
Blocktrades: accessed simply, via the steem wallet; you just need click on 'the buy steem/steem power' button and it will take you to the site.
Poloniex: used to have the best liquity, but is pretty useless right now since steem withdrawals are disabled
Bittrex: very good Exchange and I would recommend.
I haven't tried blocktrades myself because I like to use a traditional exchange because I can see the liquidity. But I guess it might be the simplest way to get steem if you aren't needing to buy very large amounts! Hope this helps.
RE: STEEM: Technical analysis: Nice recovery from downward spike on poloniex