Rework Firststrike Bracelet

Current effect:
```
The first ability you use in each battle deals 600% more damage.
```

This is fine, but there is a problem. This item dilutes the multiplier. If you have an item that makes you do 30% more damage, that item will only give your first attack each battle around 4% (going from 700% to 730%). Instead, maybe it should be:
```
At the start of each battle, gain BLACKSTRIKE, FLASH-CHR and COUNTER.
```

Buffs are a separate multiplier from % increased damage, so giving a few very strong buffs will make this item stronger.