Hi Melanie, here's a few ideas to get you started and they even have free printables too - http://aboutfamilycrafts.com/diy-princess-party-ideas/ Hope you have loads of fun and that the party is a huge success
You could make Princess Crowns or Tiaras out of card and decorate with sweeties. You could make jewellery using sweeties too. Make paper chains using crepe paper and cutting heart shape chains, Make a castle cake and cut out sandwiches and small trifles pretty cupcakes all laid out on a pink coloured Princess tablecloth. Use pretty crocks and cutlery and Doilies too.........and ofcourse Balloons.........
Here are some ideas from pinterest https://www.pinterest.com/pin/201676889549522433/
Hope you have a great party!
DollR store get tulle paint it pink get crowns balloons you should be able to get almost everything at the dollar store be creative go down the wedding isle you might need to spray paint some things