With what I know about how easy FG are to get for new players within the first 100 days (Including the new 10, 30, 50 100 day bonuses) what option you choose to spend them on is not that important. From a beta players perspective however let me say this... Adding more slots for girls is well worth the investment.

As for gatcha, I find that I get a 5* 90% of the time if I roll my 10+1 roll just after a new event and thus the new gatcha has been released (within 1 day of release). Almost every time I have rolled a 10+1 at a time NOT near release it has been bad with no 5*.

Could just be RNG but to me at least over that last year of playing that has been the trend.