The cursus honorum was certainly not the best way to enrich yourself in Ancient Rome. It was a way to turn money into political power, what of course would in return fill the treasury with even more money, provided one was successfull.

On the lower levels there was a fair chance of making some money what always depended on the superior magistrate (the one with the Imperium). The Aedile was in fact the office with the "negative balance guarantee", and many ruined themselves on their way to Praetor.

Senators beeing in dire depth, despite the income requirements to become Senator in the first place, was in fact a serious problem. And no doubt that corruption was the logical consequence of it. Caesar is in fact a good example of the monetary pressure many newly elected Praetors had been in to plunder their provinces. That did certainly not add to the stability of the Republic. On the other end we have an example like Marius who really bought his way up to the top, as a nobody with nearly unlimited money.

Another example would be Pompeius, who was in no way member of the traditional ruling class of the Republic but used his money to field an army on his own expenses and hired this army to the Senate in return for political power, like becoming high commander in Spain without even beeing Senator, leave alone Praetor.