Help Please!! I Need Ideas For My Sweet 16th

I was planning to have my sweet 16th in a hall, but it will end up costing to much so i cant any more. I cant even have a party in my back yard as it is only a slab of dirrt since we only just moved in. I cant have it at the beach or anything as its july and its means it will be ranning during my party. (i live in australia)
I despratley need ideas or im thinking of just forgetting about having a sweet 16th and missing it all together.