When I was a kid, for one of my parties, my mom made homemade bean bag game out of scraps of fabric and of course, beans. We played with those for several years after that.
We played a variation of pin the tail on the donkey. You can make something up that would be fun. (Put the party had on a picture of the birthday girl, etc.)
You can also make easy homemade pinatas with a balloon and paper mache. An old cereal box doesn't need a paper mache cover-- the cardboard can form the base although that is a little harder to "break" since it's not as brittle. Decorate them with crepe paper ruffles and be as creative as you want. The cardboard ones might even be a fun take-home craft if you do it at the party.
I tend to get plain colored plastic tablecloths and some decorations like a Happy Birthday banner that can be used in different ways over and over again.
Someone might have already said to always check Dollar Tree first. You can get cute party supplies, bags and favors for a very reasonable price. Even the Mylar ballons are just a dollar. (Their b-day candles seem to burn really quickly though.)
I've used some of the inexpensive colorful plastic bowls from there for a lot of different parties. You could even get a set of cheap festive plastic plates that are neutral enough to use for multiple parties.
Make cut-outs of the theme/characters or even the birthday child and guests and make those cardboard criss cross stands at the bottom where you cut a slit on the bottom of the picture and then a slit on the cardboard cross pieces and then put it together.
My friend makes the coolest cakes from patterns she finds online. She doesn't buy special pans. They're made from cutting and arranging the pieces of cakes baked in normal pans.
I remember those doll cakes. I thought those were great as a kid! I bet you could get creative with the bowl shape in other ways too, like make a ladybug.
Old party books from years ago had so many great ideas for homemade things. They were so much more creative, not to mention cheaper than all of this prefab stuff now. You might be able to find something at the library or at Google books.
If I find links to what I'm thinking of, I'll post it.
"...for the happy heart, life is a continual feast. Better to have little, with fear for the Lord, than to have great treasure and inner turmoil." Proverbs 15:15b-16 NLT
The pessimist sees difficulty in every opportunity. The optimist sees the opportunity in every difficulty.--Winston Churchill