Jesus, I haven't touched GDAX in ages. A fun game to play on trading-exchanges though is setting speculatively low buy orders or speculatively high sell orders (assuming you have the coin to back them) during periods of high volatility to scoop up/dump coins :)
The BTC ATM's fees are a bit too high. I like them for quick conversions to cash, but beyond that, the ~10% fee is too much to really bother with.