Hi and welcome!
Please do not feed dry food/muesli mixes. They lead to selective and unhealthy feeding. Seeds are too fatty and should not be part of a balanced guinea pig diet. Guinea pigs are junk food addicts as much as humans and generally make a beeline for any fatty or sweet parts in a mix while you end up throwing away the uneaten or soiled rest. Even if pellets may be more expensive, they won't cost you a lot more because you can feed less as all gets eaten; the current recommendation is a lot less than you would expect in order to encourage your guinea pigs to eat as much hay, hay and more hay as they can. The same goes for a carefully balanced mix of veg - less but balanced is more!
Please take the time to read these guide links here. You will find them very informative and helpful. A good diet can really help you avoid some preventable illnesses, make sure your guinea pigs are as fit and healthy as possible and live longer.
Long Term Balanced General And Special Needs Guinea Pig Diets
Edible And Forbidden Veg And Fruit List With Vitamin C Grading
Pellets Or Muesli / Dry Mix?
Apart from companionship (guinea pigs are group animals that are not wired to live on their own) and plenty of space (guinea pigs are a ground roaming species), diet is the third life enhancing and prolonging pillar of wellbeing and and guinea welfare that really makes a huge and tangible difference to the quality of life of your guinea pigs.
Companionship
Cage Size Guide
Guinea Pig Facts - An Overview
You may find our new owners guide collection very interesting and useful as we cover a wide range of topics we get the most questions and worries about by new owners. They range from settling in and making friends with your guinea pigs (including a spot of guinea pig whispering), understanding them; housing, diet and daily care, enrichment and unsafe toys and cage accessories; learning what is normal and not and how to spot early signs of illness, etc.
Getting Started - New Owners' Most Helpful Guides