I tend to go through lots of wheels w/ my cars, I have a 10x8 shed that is half filled w/ various wheels & tire sets that I use between my cars. I always swap out the OEM wheels of any car I own and tend to hold onto them until I sell the vehicle, I also run snow tires in the winter and also have some dedicated track tires for 2 of the cars. I find myself buying wheels and/or tires quite often.
You've probably already worked out things like what you're willing to spend, are you willing to go w/ a used set and what your requirements are for tires. You've also probably eliminated any idea of anything chromed, w/ swirl pattern spokes, anything that is as heavy or heavier than OEM and anything not made from aluminum or magnesium. For new light wheels you're probably already looking into the performance/motorsports selections from sites like Discount Tire Direct and The Tire Rack since they will yield the lightest wheels however be aware that some of them are considerably more fragile than OEM wheels which are heavy for a reason. Investigating in something for the street that is rim rolled or even a forged wheel might be a good option, but this will also be more expensive than a typical cast wheel. There is also a difference in quality by brand; a Rota will not be nearly as good as an SSR or BBS.
This website is a good reference for wheel weights, I use it quite often since I'm always looking for light wheels:
When buying used, there are a lot of options but depending on how specific you are in your criteria your selection may be limited. Aside from the parameters of build quality, lightness, cost, etc. The mater of appearance is subjective but in some cases very important to some. Many used wheels will be curbed, scratched, pitted, and/or have some other type of damage to it that effects it's aesthetics. Wheels degrade in appearance over the course of their usable lives. The question is what are you willing to accept? For example; a show car may require new wheels since it would need to look 'good' from a distance of about 5ft to be satisfactory to the owner. For an auto enthusiast that has a car that is driven on nice days he/she may have the requirement of a wheel looking 'good' at 10ft. For a daily driver of some they might find it acceptable if the wheel looks 'good' from 15ft (others may not care at all as long as they are mechanically sound). Some aesthetic defects that you will notice when you pick up a wheel to examine it, you may never see from 15ft when you have a tire mounted onto it. You pay a premium for mint condition used wheels but may not need them if you are not looking to 'impress'.
In regards to a wheel that is bore-centric. This is preferred of course, but you can get away w/o using it on a car like the Leaf as long as you are religious when it comes to checking your torque specs (at least once every 2 weeks). If you want, for a few manufacturers of quality wheels, they sell hub adapters intended for your specific make of car that match the wheel bore since most wheels have a bore of 70mm or larger. This allows the wheel to be hub-centric. Some of these adapters are plastic and for use on a street car is alright, but the aluminum ones which are used for track applications are preferred since they will withstand the heat of hot rotors.
I am currently running a 2nd set of 5-lug S14 wheels on my Leaf w/ Zexius OHTSU tires (205/55-16). I use a set of S14 wheels for my winter tires as well and they did so well IMO that I got another set for the summer. I've had them on the Leaf for over a month and the range is exactly the same as w/ the OEM set. This is probably due to the difference in weight of the wheels since the tire I'm running is not very good, it's considerably better than the OEM Ecopias but that's not saying much.
I also have another set of 17" Motegis w/ old r-comps on them that I purchased from another forum member but I still have yet to try them out. I plan to get street tires for these an try them on the Leaf a little later this summer.