Bear in mind that I'm not an animal nutritionist** and the following is based on my experience, opinion, trial and error and I base it on the shunamite mix concept used to feed rats but tweaked for my hamsters needs. I write this to give ideas and it's important that you only continue to feed a mix if your animal remains healthy on it.
**Hamster nutritionist is not an actual thing so be wary when getting advice from self proclaimed experts. Most commercial mixes only just need a few additions to make an excellent balanced diet.
Making your own mix can be as simple or as difficult as you want it to be. Mixing a few handfuls of bird seed in a box with a small bag of Harry Hamster constitutes making your own mix just as much as buying in and weighing a series of different grains and seeds.
Why do it at all?
Hamsters love variety just like every other rodent. Pelleted foods have their place in providing the same nutrients in each bite but are arguably not necessarily 'complete' foods that vary in quality and are fundamentally boring to your pet. Rodents are not rabbits and therefore do not benefit significantly (in my opinion and experience) from a pelleted diet. It's doesn't help their teeth, their condition or their digestion and selective feeding can be solved in other ways that I talk about in the respective care sheets.
What is in a mix?
As above it could be anything but your basics are 50-60% of commercially made food (i,e, harry hamster) and then 40-50% added extras that will be split between seeds, animal protein, grains and 'others' (like nuts, vegetables, fruit). You build your mix based on your hamster's needs. Need more body, add more protein and seeds. Need a shinier coat, add more linseed. Need to lose weight, add less protein and seeds and bulk out with dried veg for example.
Within those very general categories you can then be specific to what you can obtain. You might prefer to use dog kibble for animal protein, or you may wish to use mealworms. You might use pigeon conditioner for your seeds or you may customise a seed mix based on even more specific preferences such as linseed (either golden or brown depending on what you can get hold of), hemp, aniseed, pumpkin seed and dari mix. Whatever you choose to use, you must stick to that while mixing up all the food together and not change half way through.
Remember that corn, peas or other parts of a commercial mix are not harmful and should not be picked out. You upset the balance of the complete muesli and there's really no need to do it. Diabetic hamsters can benefit from molasses free food but you don't need to reduce the sugar in a muesli to prevent diabetes as this is not how the disease works. You can read more about diabetes on the Vectis Hamstery website
What about 'straights'?
I don't recommend a straights diet for hamsters and certainly not for pet owners. Unlike rats, there is no nutrition book for hamsters that details the individual recommended allowances for different aspects of the diet. Also, unlike rats, a hamsters dietary needs are different. You also might need to tailor your diet to different species. Ultimately, a straights diet cannot be considered balanced or complete and is best fed as a compliment to a commercially prepared muesli. Always remember that if you do choose to feed straights that you must supplement with vitamins/minerals frequently.
Examples of a Home Made Mix
The mix I recommend to pet owners is :-
1 small bag of Harry Hamster 1 small cup of mixed wild bird seed
1 small cup of mealworms or dog muesli/kibble
1 small cup of any ONE of the following - barley rings, dried pasta, no added sugar rice puffs, chopped dried alfafa, dried vegetables (not onions), pine nuts, pumpkin seeds or similar.
You can buy things like alfalfa and barley rings for horses if you have the space to store large bags. Alternatively you can order small bags of the above from Rat Rations online. If you have more than a couple of pets and/or wish to make up a bulk mix please read on.
My current mix fills a 160litre Wham box. I'll give you the quantities for this along with the proportions of the mix so you can judge how much to buy.
To fill a similar sized container you will need:-
2 large bags of hamster food. I use Mayfair Hamster food 15kg each - I buy mine from Feedem online at the moment
1 large bag of dog kibble/muesli. I use Original Vitalin working dog muesli 15kg - can be bought almost anywhere including Pets at Home 1 large bag of pigeon conditioner or budgie tonic seed. I use Bucktons Pigeon Conditioner 1 large bag of general bird seed. I use Bucktons Best All Round Racing Pigeon Food 1 large bag of extras. Currently I use either Dodson and Horell Barley Rings or mealworms depending on how much condition my hamsters need.
1 large bag of Dodson and Horell Build Up Cubes/muesli - These last four can be purchased from Feedem or Milbry Hill online at the most competitive delivery charge and overall price. You can alternatively buy the horse food from Kitnocks Farm in Botley locally.
If you wish to fill a small tub you will need to buy 1 bag of each in any case, it will just last you longer. You can still use the following ratio.
To get our ultimate 100% mix it's best to break it down into scoops. 1 scoop = 10%. So you want 10 scoops in each mix. It's very difficult to hand mix food in a large box so use a smaller tub, around 24-36l Wham to mix it up in. The scoop size doesn't matter as long as you don't change it part way through. I use a generic food scoop that I picked up at Kitnocks Farm. You can use anything you have to hand.
5 scoops of the hamster food 2 scoops of dog food 1 scoop of pigeon conditioner
1 scoop of pigeon seed
1 scoop of build up cubes
I then throw in two handfuls of barley rings to every small tub mixed.
When filling your 160l box or similar, simply repeat the mix in the small box until the larger box is full. You should keep going til both bags of hamster food have been used up. You'll be left with half bags of the pigeon food, conditioner and build up cubes. Your barley rings will last a while. You should even have some vitalin left over. Make sure your opened bags are folded over thoroughly to avoid them attracting moths.
You can also sprinkle on some chopped alfalfa or dried grass if you so wish but adding dried veg in other forms is very costly at this volume. As are nuts. I tend to give nuts as an ad hoc addition throughout the year and offer fresh veg in the week. This mix is heavy on commercially prepared food so the hamsters nutritional requirements are more than catered for.
As at the start. Increase the hamster food and decrease the vitalin if your hamsters gain too much weight. This mix has proven to be universally accepted amongst my species but you need to lessen the protein content if you feeding any male mice or rats. The gerbils also appear to do well with this mix.
Where to buy your ingredients?
Any online pet food stockist. Check horse food/bedding suppliers who often carry bulk bags of other food. Phone around your local farm shop, aviary stockist etc too as they'll often carry items at a discounted price because they order in bulk. Locally this means places like Titchfield Aviaries, Kitnocks Farm, Botley Mill and Longacres Feeds. I'm sure there are others. Reliable online retailers in my experience are Feedem, Millbry Hill, GJW Titmuss, Rat Rations and Pet Supermarket. Just be aware that Pet Supermarket aren't always clear on stock availability so if your order hasn't arrived then email them to poke them. They are very good at resolving stock issues though. Feedem and Millbry Hill are both quick and cheaper on postage at the time of writing (April 2017)