Ok, this is my area of expertise. And I have bought on (too) many occasions Ibanez guitars on Ebay, and have not been yet disappointed. Well, There are many things to consider, an the first thing to do is to go to your local music store and have a look at what's available or get a catalogue with prices and look at the current models to have an idea of what type there are and compare with what's on Ebay and older models.
If you're a beginner and know little about guitars, Ibanez is a safe brand to go for, especially in the cheaper models. Avoid eBay cheap packages of weird brands available, many are so nasty it's not even worth the postage cost.
Decided to go Ibanez? Then, here are some tips to help you decide on your purchase... Decide on the features you want: How many Frets, Fixed Bridge or trem, type of neck, pick ups. Match this to an ibanez model. Go to your music store again and try one if possible. Decide on your maximum bid. Get email alerts on Ibanez and model. Wait. (This is the part where patience brings great rewards)
When one appears, within price range, ask seller the following: Condition. Fret wear. Neck warp. Modifications. Pick Up originals? Cracking electrics? Current string gauge. Playing action. How is seller planning on shipping item safely. Does seller do escrew or COD. And finally Model No. (Which gives you its factory location and year of manufacture - see Ibanez Registery online for more info)
Never buy from China and beware of fake ones (Jems especially - I identified an obvious one eBay - wrong hadle placement, side saddle displacement, impossible serial number etc - , $1 no reserved, tried to warn eBay and bidders but too late, sold for $2300!)
Also, if shipping from overseas - Avoid cheaper surface postage, takes too long, cold/heat exposure can result in severe neck damage! Even non-Pressurised air cargo won't affect it near as much.
Finally, do not bid your maximum bid. Leave some money in your bank in case the guitar needs modifications, professional adjustment or ... repairs!
These are some of the basic rules I followed, which seem to have worked well as all my ibanez puchases have been very happy ones!