Don't be fooled by million dollar back test results.There is no way exchanges can handle trades worth thousands of BTC  without seriously disrupting the market and price. In back tests, every trade is a success, in a real live market it's not that easy. Look for a bot that has a smart trading mechanism. A good bot will try multiple limit ordering attempts, within seconds, to make a trade.  And even then, making a trade in the real live market depends on the available volume. If a bot wants to buy, there has to be enough BTC's at a certain price available. If thats not the case the trade can simply not be made or at a much higher price.

So if you want to trade with bots, use a modest amount of money and be happy with 10-20 percent a month, which certainly beats that what you get in your savings account at your bank. And also realize that there are always risks involved, not that you will loose all your money, but profits can be disappointing compared to the back tests, aspecially if trades can't be made.