You should definitely get two. They do better in pairs. You should also consider adopting (versus buying from a pet store where the pigs might be sick/pregnant/missexed) and research into the C&C cages. Guinea pigs require a lot more space than a standard pet store cage allots.
Make sure you do as much research as you possibly can, and don't stop researching after you get the pigs. Research breeds interest. https://www.guinealynx.info/healthycavy.html