as for powercreep, it's not gonna happen very fast. it took a while before new LR's completely replaced the old. the one's that were power creep were the EX versions. EX-LR, EX-UR and EX-SR were apparently really good and that stuff came after i quit. i quit after 1 year anniversaury so we don't have to worry to much.
not much reason to heard silver medals. the best you can get is HR with them. some events do give you double points when a specific HR gatcha unit is in your team. i dont think those specific units are part of the general pool and could only be gotten by gatcha tickets, but i could be wrong. same goes with gold medals, there are some events where a gatcha SR would give you like 3 times the points (points may not be exact, it's been a while).
that's up to you if you need a card or not, but i can tell you that the R's that boost or decrease by 300, 600 or 900 can be turned to medal right away. same for those that boost by 12%. those are pretty garbage. don't scrap the original 3 leaders, their stats might not be good, but they are easy to max. meaning you can have a really early 30% booster for a faction.
you may be on to something, for the price of $60, that's 60 single summons. might load up another $20 into my account for another 20 summons and see if i get lucky. though it has a much lower rate so i wouldn't hold my breath.
edit: put in $20, now won't regret if i don't pull anything good. a lot of good cards come from event rewards believe it or not.
and if i can let you guys in on a little secret, i love the pregnant cards, as i have a pregnancy fetish. sadly i think almost all the pregnant cards are in the gatcha. though there is a HR USF pregnant fencer who might be in the pool already or gets added really early. i remember having her in my DMM account. so that will probably be the easiest one to pull since i can get her with medals.
edit: first card, R Eyfaal. that egyptian looking girl. well, into gold medal she turns lol.