Use this cheat when you get the option of going into
the Senate.

Click the Emperor icon in the Senate. Give yourself
a wage of 500 denarii (Caesar's wage). After a few 
months, when you accumulate about 3000, go to the 
same screen and press the "Give to city button". 
Click the "all" button in the dialog. Then press the
"give" button. Notice, now you don't have any savings
at all. Nevermind ;) Press the "Give to city" button
again. WARNING: DO NOT PRESS THE "ALL" BUTTON AGAIN
OR YOU'll GET YOURSELF INTO TROUBLE!! The quantity
of money to give to the city is the money you gave
before. So you just press "give" button again, and
your savings go in minus, but who cares 'bout them
anyway :) So just keep repeating this and you'll 
have a fortune. And yes, don't be afraid to turn 
off the Senate screen. You can turn it off, and 
return to it later to give yourself more money.