For inexpensive but really nice phones I've had good luck with Blu phones. Can be used with any GSM carrier, or just as a stand alone device with no carrier. Bought my son one for Christmas (Blu Energy X) with no phone plan and just put google voice on it so he could call/txt/mms like a regular phone when he has a wifi connection. There is an Energy X 2 now not sure what the difference is https://www.amazon.com/BLU-Energy-Ba...s=BLU+ENERGY+X
Also features a pretty huge battery (twice the size battery than is in my phone) and great camera too.

I pay $10 / mo for an airvoice plan (they use ATT) works great on that phone, but you don't need any plan at all.

I'm not crazy about the newer android versions though, seem to be a bit more fiddly to use compared to my older 4.2 version