It is not possible to reduce RAM usage of
geth or any other application for that matter. Simply starting a
geth node will not consume much of your RAM, but when you start running commands to create accounts, send transactions etc, you can observe a spike in RAM usage. Syncing a lot of blocks at once might also need more RAM.
However, you need low-end devices like raspberry pis and system with low RAM to observe such fluctuations. With just 2GB of RAM, it's better if you don't run
geth at all because you wouldn't be able to use your system efficiently for anything else. Also, you can forget about mining. It's suggested that you need to have atleast 4GB of RAM to seamlessly start mining. At least, that's the case in a private blockchain.