'Ideal' is underdetermined here, but we could give it content. I can imagine four basic families of ways to evaluate an epistemology (in addition to combinations):

1. Territorial: How useful is the epistemology for causing agents to consistently assert truths and deny falsehoods?

2. Epistemically Rational: How useful is the epistemology for causing agents to believe things in proportion to the strength of the available evidence? This may be a special case of the territorial evaluation, defined so as to exclude gerrymandered epistemologies that only help their agents by coincidence.

3. Instrumentally Rational: How useful is the epistemology for causing agents employing it to attain their personal goals?

4. Moral: How useful is the epistemology for satisfying everyone's preferences, including the preferences of people who may not subscribe to the epistemology themselves?