I just happen to have terrible reception on some towers downstate and would like to try and receive some radio systems that are very far away (60+ miles). The area of Newark that I am in is known for terrible reception as it dips down and has lots of trees and other obstructions.
Also I think a dish looks cool, but that's not the real reason I'm interested in it.
If you don't think I need the amount of gain I mentioned, how about if I chose the smallest dish with 10dBi gain. The dish looks about 12-14in wide and weighs 4lbs? Or is using a dish technically overkill?
If what you say is true, a super large gain antenna may not help you much. A gain antenna is only helpful if there's some signal (over the noise level) for it to capture. If you're in a low spot with many obstructions to block the signal and/or trees or other things to absorb the signal there may be nothing much left from that far away but noise. With that large of a distance, you'll also be fighting the curvature of the earth, at least to some extent, causing the height issues and signal loss to be even greater.
What you may need to work on is height, not antenna gain. That would put you above the obstructions and up where there may be enough signal to capture. You'll not only need to get above the trees, but over the obstructions as much as you can. That height will probably require a very good quality coax (think Andrew Heliax like LDF4-50A -
Heliax Coax - LDF4-50A or better) to reduce the associated coax loss.
Your situation may be similar to you standing outside of a soundproof studio watching a band play inside of that studio. The soundproofing (like your low location) keeps the band's sound from being heard by you, even if they turn their amps up quite loud (you using a high-gain antenna). Now if somebody happens to open the studio doors (you getting your antenna where there's enough signal level), you can hear fine.
A high gain dish is used to provide not only gain, but even more often a narrower beamwidth. A yagi may give you a 20 degree beamwidth while a dish may only have a 5 degree beamwidth. This is often necessary since microwave links are generally point-to-point and the frequencies are reused for signal paths going different directions. With a large dish, you would need to point the antenna very accurately (and hope that the wind doesn't blow it off course) while with a yagi, you need much less accuracy when pointing the antenna.