Find a herald to reduce your notoriety and bribe him. This will cost 500 florins. Once done, immediately steal from him. You will get the 500 florins back, plus 3 to 5 extra florins. Repeat this one more time, with the same or different herald and the achievement or trophy will be yours in a matter of seconds.

Go to Florence and look for a large group of people. Your goal should be to have those people walking towards you. Hold the X and walk through this group of oncoming people. You will pickpocket most of them in a matter of seconds. Because that button also serves as the "fast-walk", you can quickly get florins from citizens if you keep it held.