Talk:Ensemble Stars! Master Guide/@comment-25148607-20150805233121/@comment-26428369-20150806003154

You can get them during any produce, but it's mostly random. Your best chance is to do the daily jewel-boosting produce and use cards that have jewel-boosting lesson skills (it'll be something like ”全ジュエルの＿＿＿が少しアップ” on the card page, adonis with the grocery bag is one such card). And then do produce over and over until you have enough large jewels...

If you want a certain color look for card skills that replace 全 with the color you want, and produce on the day that that color is in the daily produce.