Rather than overfilling their cage with toys, have fun with enrichment time - especially at dinner time. This allows you much more to vary and stimulate their brains. Choose huts and log tunnels with two exits so piggies can zoom through them; at least one hut or log tunnel per piggy. It also mitigates dominance behaviour whenever they have to establish/re-establish their hierarchy. chucking an underpiggy out of a prime spot or hogging a bowl is typical dominance behaviour whenever piggies settle in, so you can neatly work around it.
Sprinkle their 1 tablespoon of pellets per piggy per day and their daily veg aroung the cage to encourage natural foraging behaviours, have them come to you for the first bite and make them work for their food. Keep in mind that pellets and veg only replace the supplementary role of wild forage and that over three quarters of what piggies eat in a day should be hay. This also avoid your piggies messing up bowls by turning them in their preferred water closet. The more hay they feed between meals, the better - it boosts health and can add 1-2 years to a normal life span.
Long Term Balanced General And Special Needs Guinea Pig Diets
Enrichment Ideas for Guinea Pigs
Here are some very helpful links to practical information collections for Wannabe and New Owners to help you to a good start:
Are Guinea Pigs For Me? - Wannabe Owners' Helpful Information
Getting Started - Essential Information for New Owners
On a very personal note: PLEASE consider adopting from a good welfare standard rescue rather than buying. Not only can you neatly avoid all the usual pitfalls that await the unwary but you are also helping with the current unprecedented pet dumping crisis and are making space for more piggies in need of expert care. As a new owner, you will also be matched up with suitable piggies for an easy start - not necessarily babies but piggies that are used to handling and human interaction so you don't have to deal with wiggly babies that are already teenagers by the time they have settled in fully.
Rescues (Adoption and Dating), Shops, Breeders or Online? - What to consider when getting guinea pigs
New Guinea Pig Problems: Sexing & Pregnancy; URI, Ringworm & Parasites; Vet Checks & Customer Rights
Boars, sows or mixed pairs; babies or adults?
Guinea Pig Forum recommended rescues