Other forms: goodliest; goodlier
A goodly amount of something is plenty of it. If you bake a goodly number of brownies for a bake sale, there are more than enough.
The adjective goodly can describe a large quantity and also a large size: "You described your house as tiny, but it's actually a goodly size!" You might bring home a goodly amount of spinach from the farmer's market, or take a new job that comes with a goodly increase in salary. Goodly comes from an Old English root word, godlic, "excellent, good, or fair."