You can cut costs by making things yourself, finding free patterns all over the internet, using old clothes for fabric but for those without such skills there are other options.
Finding other dolls that have the same proportions as your chosen doll and using clothes designed for them.
Yo-SD dolls will fit many fashion doll clothes such as barbie and Moxie teenz.
MSD or SD dolls will fit Best friends club doll clothes though these will be very short.
Just see what's out there.
Jewellery can be another thing that turns out to be more expensive. A great tip is to check out your own jewellery box for old necklaces, bracelets and general stuff that you don't wear any more. A pair of pliers can be your best friend.
These little accessories were made from the details of an old choker. For furniture you can create from scratch, trawl antique shops or modify other doll furniture. I prefer the latter.
Out of a doll cot I made a bed and sofa with a ladder for my smaller dolls. I also have a wooden doll wardrobe that holds a lot more than you'd think.
Doll ownership is fun, and so it should be, but it is expensive. Save where you can and you won't regret it.
