the guy said in order to do the proper setup it would be necessary to use capacitors. So my question is would it really be necessary to do this and if so where would they go?
the only difference is that I would e using a 9 volt battery to power the motors.
The motor supply (as opposed to the logic supply) benefits from big decoupling (1000uF or similar).Especially if the supply is weak and can't supply stall current. Decoupling the supply also reduces EMI radiated from the battery connections.
I strongly suggest you use a different power supply.