The best surface is ice, if you can create your own lil ice rink.
Well, I was in your shoes, and a shooting pad (actually I got a tape2tape), a goal and ~30 pucks was one of my best investments so far in hockey. Actually any kind of hard, relatively slippery surface (PE, plexi, etc) will do, you can also use some kind of lubricant (I used silicone) to make it more ice-like.
You still need to adjust a little bit, when you get on the ice, but your mechanics and technique will be much better, so you'll see a big improvement.
When I started I used to shoot ~300 pucks a day, mostly forehand, now I shoot ~500 / week, and it's more of a wrist, snap, backhand, one-timer, slap festival, whatever I feel like I need improvement on.
Do it, you will not regret it.