Can you really be sure you will profit unless you have insider info?
Not at all. Trading with bitcoin requires you to follow the price flow, current events that might change the price and also a little luck.
But simply, all of this information is just making the guess / choice you're making more educated here it's not like you're going to be able to have better luck on the workings of technical analysis it's still going to be the same guess that someone could have if they were just monitoring the coins news itself / bitcoin in this case.
Trading and Gambling are close in nature when you think about it, the two of them attempt to get people to take guesses to see if they can make some money off of this The only difference between the two is that in trading you can minimize the chance of loss of funds though.
But I'd still says it educated guessing, as ANYTHING could happen in the market and you'd never know what the fuck just happend if you're not one of those whales that could pull some crazy stuff off by themselves.