The Moto G or the Moto E are really your best bets. Unlike many other low-cost androids phones, these are not generations old left overs. No, the specs are not as good as a flagship phone, but you do get the benefits that matter: Quad core CPU, decent displays, and good battery life. Both the G and the E are running the latest major release of Android too, Lollipop. Motorola also uses a near-stock version of Android on their phones which, IMO, equates to better user experience and battery life.
I personally think the Moto E is a great option for a backup/low-risk phone. It is small, packs a 2300mah battery and is solidly built for US$120 off contract direct from Moto and no Carrier bloatware apps installed.
If you are looking more for a daily driver, the Moto G has a much better and larger screen, a decent enough camera and runs US$180.
If you want more flagship-like features, the current generation (2014) Moto X is really not all that bad at $399 off contract, which is very cheap compared to other flagships. I had the previous (2013) Moto X and upgraded to the 2014 model. They are both amazing phones. The cameras leave a little to be desired, but in every other area they are excellent.