Yes, the .124% Legend drop rate does apply to the "natural" rare gacha that you can get free via medals.
I definitely can't argue against how clunky and inconsistent a lot of the descriptions/help/wording in the game is. Along with the interface, that's what kept me from really getting into it in its first few weeks. I was lucky enough to join a helpful guild right off the bat and the sharing of knowledge helped a ton--there was no way I would have figured out most of the stuff I learned faffing about on my own.
As for prices, you'll get plenty more value out of specials like the Fever gacha or even the Sugoroku slot that's up now. Buying the 1500 gold lucky bag will give you a 10 draw with lots of exclusive SR and SSR in the pool, plus you'll move spaces on the Sugoroku board as well from which I believe you are guaranteed at least one of the new SR even if you get the minimum 40 steps. If you're lucky you can clear the first sheet right away and get one of the new SSR. The Fever gachas are an even better value if you're looking to not spend so much. You usually get a free ticket anyway, then they start at 300 gold and have really good odds of nabbing at least an exclusive SR.
PPS: 3m+ SED
Hitsuji: 85 Nina