Tomorrow is Parents' Day. Did you prepare carnations? --.Tomorrow is Parent's day. Did you prepare the carnations? 

Oh no! I forgot. I should buy it, too. --> Oops! I forgot. I have to buy them, too. 

But I don't have any money. Can you lend me some money? --> But I have no money. Can I borrow some money? 

=> Your sentence has a correct grammatical structure, but this has the correct usage/ expression.