Check out a standard ham 2 meter antenna. They aren't too expensive and fairly easy to put up. Most have some gain, which should help your receiption over ones that don't (more gain generally = more signal to your radio). Another thing to do is use some good coax on that antenna. RG-58 or RG-8X (aka RG-8 mini) will make your gain figures nearly go away so use some good coax like RG-8, LMR-400, or RG-213. You'll also need some lightning protection so make sure you get that as well.
If you have someone make up your coax for you, let them know not only the lengths, but also what connectors you'll need on each end (they don't have to be the same). If your antenna uses "UHF" (aka PL-259/SO-239) make sure that the antenna end gets one for that end. If your lightning protection uses "UHF" than make sure that the ends that'll connect there have those. For your scanner end you'll probably need "BNC" on that end. Often that'll leave you with one coax with "UHF" for the antenna to the lightning protector's "UHF" and another with "UHF" for the lightning protector's end and "BNC" for the radio end. If necessary you can often get adapters to change things if you don't get it right, but they'll reduce your signal and provide an entry for water to ruin your coax run. Since you're starting out with nothing, you can easily order everything correctly and eliminate the adapters.
A dual band antenna will work as well and add the UHF (400 MHz frequencies) as well. Standard Scanner antennas will work too, but generally won't give you any gain since they're so wide band (they'll do better on 800 MHz, but your area doesn't use it so why get lower gain where you need it to cover a band you don't need).
Some places to check are:
http://www.texastowers.com/online.htm
http://www.hamradio.com/search2.cfm
