Planning a trip to washington dc and need a bit of help?

I am planning on going to washington dc in 2 weeks, just for the day. i'm wondering how much money i'll need to go. I live in south jersey and plan on stopping in VA for the arlington nantional cemetary. Here's what I want to do: leave about 7 am and get there about 10 am. visit: FDR and Lincoln memorials. Smithsonian air & space museum, natural history, american history. vietnam vetern's memorial wall, national zoological park, supreme court (maybe), us holocaust memorial and washington monument. I'm thinking i'll spend about $60.00 in gas and i don't know what else. I don't plan on seeing anything that isn't free but i don't know about parking or food or anything. thanks for the help!