The config file in Gunbot does not account for exchange fees. So if you set your config to 1%, you'd only get a profit of .5% as you'd pay .25% for the purchase and another .25% for the sale. Gunbot only looks at the purchase and sell price... it's up to you to setup your confit to account for the transaction fees.
It varies by exchange, but for Bittrex, I've calculated it at a minimum 0.54% profit needed on a trade to break even.
In Microprofits strategies, I've always used 0.8% as the baseline minimum to sell for, or all you end up doing is making the exchanges a tidy profit from your fees, greatly outweighing your own profits.