Everyone is kind of dancing around it, but I'll come out and say it. Unless it is an old used one and proven good, don't buy a Gamo.
Also, don't buy based on manufacturer's velocity claims, as they test with 4.5 gr. pellets, which is not what is used in reality. Sometimes, they'll be realistic enough to publish a velocity spec with lead pellets too, but then, assume that is the 7 gr. wadcutter pellets, which is not what you'd use for hunting.
What's your maximum budget? Folks always come into this wanting to spend around $100-150, but they don't realize that a $150 spring gun (gas spring or steel spring) is not even going to be as accurate as a typical Crosman 2100 that costs half as much. At that price range, you're generally trading accuracy away for power.
My advice is either for a Benjamin 392 (a high end pumper) or a mid-level German springer. (Diana 34 or Weihrauch HW95 (which is the less expensive version of the Beeman R9 pictured above) For something worth keeping, you'd be looking at maybe $250 + $110 for a decent scope and rings that would let you get good accuracy out of the gun.
If you need to keep the budget down a bit more, a tuned Chinese springer from Flying Dragins Air Rifels could be good, or better yet, a used-but-not-abused German springer.
I just traded my old Stoeger X20 with aftermarket trigger away to a friend, or I'd offer it to you for a song. That gun is good mechanically, but had a CRAP trigger, which robbed it of 50% of its accuracy potential. It's a common complaint for entry level springers below about $250. That, and the included scopes in kit deals are also crap. (can't take the recoil)
I'm not sure what the deal is with ^ these characters offering you $700 PCP airguns when you mentioned you're looking at $100 ones...