If you want to buffer your water, you need an idea of what your hardness is. There are several ways to alter pH/hardness. Substrates work well for making the water harder and increasing pH. Baking soda, but you need a test kit to keep things consistent. Crushed coral, some rocks (texas holey rock as an example) are other methods.
To soften your water, you can use peat (or peat granules), or some substrates (ADA amazonia will soften water but is quite expensive). Adding driftwood or almond leaves can make minor differences in softening things up as well.