Panama City has the old city, the canal, parks. You probably would want to go to other parts - beaches ? Or mountains ?
How much money - depends a lot on what you do !
I've been to Panama 3 times i mostly go to the countryside and that's were you should go if you don't have that alot of money because in the capital PANAMA CITY is expensive since every thing is in dollars just like USA
For how long will you be there? I have been there twice and I think there is nothing fun to do in the city.. it's just a city. You should totally go to Bocas del Toro. Google it. you are going to love it.
Go out to the Coronado area. Coronado, Gorgona, Santa Clara or even out to Pedasi or Las Tablas.
I'm gonna go there around June just me and my boyfriend is it fun & nice out there how much money would I need all together