Guinea pigs must be kept with other guinea pigs. That's rule number one. They are herd animals and so even if you can spend lots of time with your pet, they’ll be unhappy without a guinea pig companion.
Two sows, two boars, or a neutered boar and a sow, are all good GP combinations. Larger groups are common too, although that requires space. Once you’ve bought the materials needed for two guinea pigs, scaling up is pretty easy, and not too costly. Hutch space is the only issue.
A happy group of guinea pigs, of the ‘skinny pig’ breed
A hutch or run built for two guinea pigs won’t be big enough for a larger group. Each guinea pig needs about three square feet of space to, and the more space you can supply, the better!