I haven't made any plans for tomorrow. I'm going to take it easy.
Literal
Tomorrow [possessive-の] plan [topic-は] stand-not [progressive-ていません]. Carefree-do [volitional-つもり] [polite-です].
計画を立てる ('to stand up a plan' = 'make a plan') is a fixed collocation — 立てる literally 'to stand up [something].' 気楽にする uses the adverbial form of the な-adjective 気楽 + する ('do X-ly' = 'act carefree'). ~つもりです expresses a personal intention.