You need to purchase a number of things before getting a hamster so that everything is ready for him or her. It's not a good idea to bring a hamster home before getting a cage!
A note on "Starter Cages" - I firmly believe that
"Starter Cages" are an absolute con and all they do is make is so that
either a hamster lives a life in a tiny, cramped cage or the owner has
to fork out a load more money once the hamster outgrows the starter
cage. It's much cheaper and more sensible to buy a cage that will be
perfect for the entire life of a hamster.
Anyway, here's a checklist of things you will need, plus a few extra bits and bobs.
The RSPCA recommend that cages should be at least 75cm x 40cm,
Syrians are better in 80cm x 50cm cages Dwarfs can go in cages slightly
smaller (depending on the breed and the hamster). Levels and different
compartments do not count towards this measurement - this should be the
minimum footprint of the base of one cage.
Syrians need wheels that are 10inches or larger, 8inch wheels are
good for all Dwarf breeds, although the smaller Roborovski hamsters and
smaller hybrids are fine with 6inch wheels.
Water bottle or Bowl
I much prefer bottles to bowls as there isn't any risk of spillages or substrate/food/poo/anything else getting into it. Classic water bottles seem to be the best out there and they aren't very expensive either.
There are about a million different houses out there, plastic ones, wood ones, ceramic ones, cardboard ones etc. I've tried wood and plastic but do you know what my hamster currently sleeps in? A cardboard box. Tissue boxes are great for houses! A lot of hamsters do have open nests though so if your hamster doesn't end up using the house I wouldn't worry, make sure they do have access to one though (and that its big enough, some aren't big enough for Syrian hamsters).
A good layer of substrate is needed in the bottom of a hamsters cage, there are plenty of options out there from the well known option of wood shavings (ensure its dust extracted and kiln dried) and the more expensive Carefresh which comes in different colours. Whatever you choose it's best to buy it in bulk if you have the room to store it as it will save you a lot of money!
NEVER, ever buy cotton wool/fluffy bedding. It's highly dangerous and can cause all manners of injuries and illnesses. Safe nesting materials include shredded jay cloth, shredded paper and the home made variety - shredded loo roll. A large handful should be given each clean out and replaced in between if needs be.
As with other rodents, hamsters teeth constantly grow. This means they require things to chew on, whether wooden chews or wooden toys it doesn't matter, as long as they have some wooden things to chew on. Make sure that they are hamster safe - a twig from the back garden isn't suitable.
This is an absolute must for cleaning the cage - you can pick up pet safe cage cleaning sprays from pet stores and you can also buy pet safe disinfectant wipes which are just as good.
A good quality, specialist hamster food is an obvious must.
Some people are completely against using balls - its unnatural for a hamster to be locked in a small ball etc but a lot of people use them and their hamsters seem to like them. It really does depend on the hamster - if a hamster refuses to walk into one then don't force them, if, like my Luna, they will sometimes refuse to come out of the ball then its fine to use them. Ensure that the ball is big enough (same principle as wheels).
Hamsters need "floor time" - in other words set up a secure space with toys etc for them to have a run around in. You can get specialist hamster playpens for this but be warned - Syrians can climb out of most of them! Things like children's paddling pools, large cardboard boxes etc can be used as a (often cheaper) alternative.
If you love hamsters you're unlikely to be able to buy hamster toys for your beloved pet - bridges, tunnels, climbing frames, grass balls - the list is endless.
Toilet and Toilet Litter
Hamsters are very clean animals and 99% of the time have a "wee corner", this can get quite smelly very quickly though. Providing a toilet with special toilet litter will give the hamster somewhere to do its business and the litter will reduce the smell to almost nothing. Good ones clump too which makes it easy to get soiled litter out without having the replace the entire lot.
Sandbaths are fantastic for both hamster and owner - the hamsters coat will improve and you will be able to watch them as they dig, dive and flick around in the sand. It's great to watch! Ensure to use sand and not dust - the dust ones are great for Chinchillas but not hamsters (it can cause respiratory problems in hamsters).
Fabric hammocks are a great addition to a hamsters cage - keep an eye on them when you first get them though, if a hamster chews them its best to remove them. Pouching or swallowing the fabric can be dangerous to hamsters digestive system.
Hamster treats come in all shapes and sizes and fresh vegetables, fruit, nuts and seeds also make great treats.
I apologise if I've forgotten anything... Went over it a few times while scratching my head but nothing else came to mind!
One thing I will add - ensure that you have someone who will look after the hamster when you go on holidays and that you have registered the hamster with a local vet.
Good luck with your new hamster!