I'd second SpugEddy's suggestion about the Icom F420. I used to run a few of those when I was on GMRS.
They are solid little radios and will do everything you need for GMRS. They are long out of production, but cheap on the used market. Programming software is pretty straightforward and easy to understand. It's also cheap. Programming cable is inexpensive, too. A really good starter radio that will meet your needs for a long time to come.
You can pick them up for well under $100 on e-Bay, however you need to know -exactly- which model you are buying:
There are 4 different frequency splits in the UHF models:
400 - 430 MHz. Will NOT do GMRS, cannot be adjusted to do so. Do -not- buy this model.
450 - 470 MHz. This is the one you DO want. Covers all the GMRS channels and will even cover some of the 70cm amateur radio band if you decide to pursue your amateur radio license.
470 - 490 MHz. Won't do GMRS out of the box, but I recall people being able to get them to work down around 462MHz. Still, I wouldn't recommend one of these since getting the VCO to lock that far out of range can be iffy.
490 - 512 MHz, T-band model. Won't work for GMRS.
There are also two sub-models of the F-420 line, the "S" and the non-S models.
-S models do 4 channels. That's good for a base radio where maybe you have a simplex channel, a repeater channel and one or two others. I used one of these in my house for years as a base. No LCD display, just LED channel indicators.
I used a few of the VHF versions of these (F-320S) as adjacent agency receivers in a dispatch center. Those were powered up and running for well over 10 years straight without issues. Never transmitted, but always on.
-The non-S model will do 32 channels and has an LCD display. Better suited for mobile use.
These radios will do 35 watts, more than enough for GMRS. In reality, you usually won't find UHF radios much higher than 35 watts, but there are a few that will do 45. Don't get hung up on that 10 watt difference, that additional power does not directly translate into a big range difference. You'll get more performance gains by using a good base antenna and high quality coaxial cable.
They are also FCC Part 95A accepted, so totally legal to use on GMRS.
There are also a couple of other models that work well:
F-2020. This is a larger radio, 35 watts, but will do 32 or 160 channels depending on the optional memory chip upgrade. You can also get remote head kits for these. Again, long out of production, but on the used market. Frequency splits are the same as the F420.
F221 was a newer model. There was an 8 channel and 128(?) channel version. Good radios and I used one as a mobile in my wifes truck for a few years.
F621 was a higher end model. More channels, but similar specs.
There are quite a few Kenwood models that will fit your needs, too. The TK-805 was a popular model around the turn of the century. Nice part about the TK-805d's was that they could do some rudimentary front panel programming if you needed to make minor changes in the field.
There's a lot of newer models, too. TK-8180 is popular and still in production. Not 100% sure it's got the 95a certification for GMRS, though.
Thing to remember is that the RF wattage isn't as important as many people think. New users will get excited about a 5 watt power increase, yet they'll see very little in the way of range improvements from that. In reality it's all about your antenna system and feedline. Focus more on that than the radio since that will be something you can use for a long time and it'll give you a bigger bang for the buck.