On the radius, I would stick with one location and manage your adgroups with optimization and cost per click. If competition is fierce, you will simply have to pay to get into the game, no $.10 clicks for you unfortunately. We have found that radius targeting can really work for some clients, but I wouldn't recommend changing the location frequently, remember Google creates a history of your program and this affects your quality score, give it your best shot and stick with it and manage your ads with optimization and watching your max CPC and daily budget. Steer clear of the budget optimizer and watch your account several times a day then give it about 3 weeks fine-tuning as you go.
Create two campaigns.
In the first campaign, use IP targeting.
In the second campaign, set the location to national, and then use geo qualifiers with your keywords. This will help to catch those surfers with an unknown IP address using geo qualified searches.
(i.e. orange county widgets, los angeles widgets, etc).
People search by zip codes, counties, states, metro areas, cities, area code, and regional names (i.e. bay area real estate), etc - make sure you're showing to those as well.
I don't see the point of changing your 50 mile radius everyday. If you change your location, and keep everything at a 50 mile radius - wouldn't you be advertising to different people every day, and not reaching your target 50 mile market? If I'm missing the point of the reasoning - please elaborate.
So the center of our circle is located 20 miles farther from the metro area, then our actual location.
Google recently made some nice improvements to this feature to make it easy to implement and use.
It'll let you specify your area very well.
Just remember, the area you're specifying is where the searchers IP address is located and not their actual location. So, if there are a few large ISPs just outside your range, you might want to extend it just a bit further than normal.