Playing Shards
-Because Shards is the only way to get a guaranteed SR gacha (just stick to rank 5 battles against your weak opponent), *everybody* will end up with very comparable scores until the 300-streak
-Once people get past the 300-streak, the field will spread out a bit more, since some will be able to handle rank 1 / rank 2 opponents, and others won't, some even will simply quit the event after they reach the 300-streak. But if you want to make the top-1000 rankings, you'll have to get past the 300-streak first. Preferably as soon as possible. As long as you don't clear the 300-streak, don't have hopes breaking the top rankings, unless you ignore the streak entirely (pretty dumb, it has the better rewards to get you through the event) and go for top rankings straight away.
-If you have access to ex-levels, this is the event to use them. An 11,190 SED (Max +10 Ex) Hyuga beats an 11,160 (Max) SED Hyuga ( (Taking Hyuga as an example to highlight that she's currently the highest SED MOE card)

Spending Shards
-There have been reports of shards disappearing between events. It's very possible that they are on a timer. So don't keep your shards in stock forever. Better to spend them while you have them. As soon as you have enough shards to buy a girl, get her. Stocking up on shards comes after you get the girls again.
-You can also buy some other useful stuff with shards. Generally, after I get all the girls I want, I spend half the shards I earn during the remainder of the event on stuff like reveals and ex-wildcards. So I bring some shards to the next event, but also purchase some other stuff. Even if you aren't lvl 50 yet, it's not a bad thing to stock up on some ~30 Ex-Wildcards in preperation for when you are. You don't have to buy a whole set in one event, but 2-3 during each Shards event is a good start.