You got some great advice to first test simplex range, radio to radio, for your 20 acre homestead operation.
But you also are interested in a repeater for extended range capability and allowing others to use it. Before you put down a chunk of money on a repeater, see if the friends you want to talk to are also in simplex range. If the Gillette topography allows for it you might get some good extended range on simplex.
However, if you are in a rural area, making contact with more distant friends, or if you want to keep in contact with family when they head to town, a repeater may be required. Looking at the GMRS repeater map I don't see any repeaters covering Gillette. But there may be some unlisted repeaters in the area you can discover when settled in.
If you go the repeater route, you will find good information and advice here on brands, costs, build tips and reasonable range expectations. Of course You Tube has some good stuff. Repeater-builder.com has some valuable information as well.
As far as coverage, Scadacore.com has a line of sight map which will give you some very general ideas on what you might expect for effective radio to radio communications. All based on each radios map location, the topography between the two, the ground elevation of each unit and each radio's antenna height above the ground. It's not perfect, but it's really easy to use and a pretty good resource.
Lastly, not are repeaters are equal. Your anticipated use, needed duty cycle (how often it's gonna be in use) and desired range will play a big part in the cost.
Best of Luck