Its all about personal preference, choose a gun that feels right to hold (ask about at events to hold or try different guns), thats cheap for you (price is down to you), and that isnt that hard to keep maintained (you dont want to be lost when you strip it down to clean).
if you can get the money, your best bet would be either an ego 05/06 or an etek 1/2, invert mini is ok but you have to strip the marker down to get to the bolt whereas with the previous guns i mentioned, the bolt and breach are easy to get to, you'll see what i mean when you hold one or see one up close. Watch what your buying, read the descriptions on them properly and always ask any questions if your not happy/sure on anything. If in doubt, ask in the buying and selling queries section in the classifieds, have fun.