My advice:
Decide the use and power you need, the the caliber you want to buy ( for hunting 25 is better than .22, .22 is better han .177) it you are going to hunt middle size game, go for a .30 Cal.
If you are just going to make target shooting at less than 90 yards, a .22 can do it.
Define how many shots per fill you want.
Buy a small PCP compressor at Amazon.
Go for the best quality rifle you can buy in order that you get more accuracy and less leak problems.
I have seen a rifle like this one that was very accurate. The power shown in "specifications" section of this rifle is really decent:
We've got a great price on the Hatsan NeutronStar, Synthetic. Get a great price and expert advice at Pyramyd for your next outdoor adventure!
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Buy a scope with many references at the reticle. Something like this:
We've got a great price on Hatsan 2.5-10x50E-SFT Scope, at Pyramyd AIR. Shop where the experts do!
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Whatever rifle buy try first JSB pellets.