not an app but here is a good resource: http://eword.ntpc.edu.tw/phrase.htm
i admire you're willingness to learn traditional characters. we call these 生字簿 (unknown character booklet) in taiwanese elementary schools, so it helps if you know 注音 (zhuyin, aka ㄅㄆㄇㄈ bopomofo), and the pages flow from right to left vertically for stupid political reasons so be prepared for smudges. unfortunately the site is designed for parents and teachers, so kinda unfriendly if you don't already read chinese, but the link above should contains all the links to the pdfs. start with 一年級 (first grade) then 二年級 and so on. it's a lot to go through and meant to take six years even for kids with they sponge like memory so take it slowly, have fun!