The level 1-20 dragon balls are attained from quests around the starting area, if you have had one drop for you from a mob thats a genuine dragonball, if your looking to find your 7th rumage around for any quests, if in your previous reply you mean your missing the 3 star dragonball, it will be quite early on in the starting area that you missed a quest.
In the case gz, yeah you can only get dragon balls at the weekend, when you hand in your 1-20 dragonballs you get a scouter chip which allows you to hunt for genuine dragon balls.