No! You can't use *A lot* - Have to start with *Lot*... Lot of increase has been witnessed in the price of precious metals in recent years.
There is no way to make a sentence with Lot unless you use it as a name. Look up Lot and you'll see because you can't say Lot without adding an S to the end or an a in front of it. So there !! Years of practice can make for perfection.