Protip: If you want to better plan ahead for the future on this sort of stuff, you need to be willing to spoil yourself looking through the wiki. Google 'kamihime project wiki'; look for the url that's mostly in Japanese but with 'wiki' as the one English word in it. Use Google Translate if you have to. On the left side, look for Other, then for Gacha. Scroll down till you see the gacha update history. Read up on who becomes available when, then figure out for yourself how many jewels you want to have by X date.