Ok, so I didn't know if this is widely known or not, but here it is anyway.

Apparently there is a way to add money to other factions(and take away money for that matter) without using diplomats.

Open up the console and type in add_money (insert faction here), xxxxx.

So an example would be add_money parthia, 40000.

Some factions have weird names you have to type in order to add money. Open up the decr_.txt in your RTW folder and there should be the names of the factions you have to type. Like the Seleucid Empire you have to type seleucid.

Alternatively, you can decrease the factions money simply by adding a - sign.

Example: add_money parthia, -40000.

That's all there is to it.