Should I get a dependent spouse visa off my wife's retirement visa or apply for my own retirement visa?

You can certainly get the trailing spouse' Non-O and then an extension of stay that matches your wife's extension if you want to. That requires no proof of funds because you're getting your extension based on being married to someone who has a long term extension..

You probably will get grief from the immigration office about it, especially if you're over 50 as well, but it's totally legal to do. They'll try to shoe horn you both into getting your own "retirement extensions" by each of you meeting the financials.

Your misses has a Extension of Stay? If you want your own Extension of Stay based on being over 50 years (retirement) you need to meet the same financial requirements. If you apply as dependent of your wife you won't need these financial requirements.