You can use a voltage regulator (practically an amplifier that is used for bigger and robust circuits) but do remember with any amplifier that you need its own source, and that the voltage output of the amplifier is never ever above the maximum voltage supplied for the operation of the amplifier. So that leads to a dead end too. Also you can't use a transformer for a homemade battery cell. You need AC for a transformer to work. Homemade batteries output DC.
What is your homemade cell currently giving for the output current and output voltage? If you are getting below 0.1 A and above 1 nA of current and a voltage below 10 V but above 1 V, then stick to digital circuits as this is perfect for you to deal with!