I've tried gold level exchanges 3 times. I have zero SRs to show for it. I experimented a lot with Ex Wilds. I meant to buy a bunch during the last shards event, but the new event started about 30 seconds after shards ended. There was no time to trade in my shards, so I start the next one with about 500 in reserve. I got all three girls, but I didn't get to buy any CRs or Ex Wilds.
Oh well. Having 500 shards in the bank ain't a bad thing. It's hard to get 1800 shards to buy all three new girls without some serious SEC help. 1300 is MUCH more doable.