I have two paddletail newts (kept in separate tanks) and though I provide floating islands and haul outs for them, neither one of them use any land. They seem to be the most aquatic of all my newts. And I think gravel or marble would be fine, as long as whatever you use is too large for a newt to swallow. I myself use bare bottom tanks, because I think this makes it easier to keep clean.
The only plants I use are pothos cuttings, I let them just float around the tank. You could also use plants like java moss, java fern, elodia, hornwort, anything that does OK in low light and cool water.
I would not feed my animals beef, its not something they would eat in the wild and I think there are more nutritious foods available like earthworms, black worms, blood worms, dusted crickets, etc. Read this:
http://www.caudata.org/cc/articles/foods.shtml
As far as their cost, I have no idea! My first paddletail was a gift from a friend, and my second I got for free from my local classified from someone who no longer wanted it.
Good luck with your future newt, and I think its great you are doing research prior to purchasing it. Please ask any more question you may have,
Heather