Absolutly! get as big as your pockets can stand!! But as you stated You have not found the tract of land yet. I was once in your shoes about 6 years ago. I have found that good size lakes and ponds are tough!! very tough!

Couple of questions where in GA do you want this tract of land?
What size tract of land?
Have you look at alot of lakes with their acreage size given? What size do you want?
Lot of questions to be answered!!!

I can tell you right now! there is alot of cheap timberland on the market in North GA. You can get it real cheap in the "East Athens" area counties. Also from talking with DNR people, it is not very hard to a lake approved. But, here is the kicker for N Ga., Topography. Most of the tracts of land I have looked at in North Ga are very steep! This really makes it tough for building a good size lake, because the water backs up and becomes to deep before it tends to spread out to make good surface acreage. Now I am not saying you can't build a larg lake in north GA but it is tough find a good larg lake site.
The places I had the most luck was south or middel Georgia, just below the fall line, where the land laid a little flatter. Now when you go to dam up a creek or stream the water will spread out over the land better and you can pick up some surface acreage.
The first tract of land I bought took me 4 years to find, it was in middel GA 8.5 acre lake, loved it but it was too far to manage. So I sold it and stumbled on a tract in North Ga that I think will make a 10 or 12 acre lake. The key when look at land here in N Ga is to find hardwood bottoms because they tend to go flat for quite a ways. In these botoms there will be a creek channel. Visualize your site with the water coming out of that channel and filling in that botom.
One other point when looking at this timberland you will always find that the timber company leaves alot of good mature timber along creeks and streams. When you build your lake you can get a permit to harvest this timber along these SMZ's and it can really go a long way in paying for you lake!
Here again I bought my tract in N Ga. and supposed to getting the lake site survayed this week for the size, were hoping for over 10 acres.
Also have a lot of timber to sell where lake is going to go.

good luck!!