Always good to start small. How about a few hills with broken down buildings? You could go from there, and maybe make it a swordfight, or a gunfight.
Good luck with whatever you build!
Well I see your new to roblox I think XD. Anyways like he said always good to start small. Maybe a sword fight or a gun fight or something and later when you think your ready you can try useing "Roblox wiki" Located at "www.wiki.roblox.com" and work your way up and maybe get some lua books in stuff. But I recommand that you don't use free models theres virus's in some of them I wouldn't take the chance. If your gonna use them take them from someone that you've meet on roblox. Any more help? Just message me.