1. You can buy a one with trashed engine and rebuild it. That's a good option that will get you a premium new engine, you can also do a bridgeport mod and turbo it meanwhile at it if you're rich enough also>what is a compression test
2. suspension is to be changed anyway, coilover is a must in any RX-8 for better experience.
3. You don't buy a rotary for gas savings.
You obviously have only a very shallow knowledge on this topic.