Once the ability starts to resolve, players can't respond to the choice or take any actions until the ability finishes resolving
So no need to worry for now, just something to keep in mind
Equip abilities sure are activated abilities
Paying life is around in the format but it isnt some huge theme, and you need to both pay life and have a card where it matters that you can reduce its cost It can ramp your mana quite effectively, and that makes it more likely that you can get a creature with power 4 or great into play quickly, at which point Ruby herself becomes a significantly better attacker
Whether youre digging for ramp, utility, or combo lands, this little cleric puts in serious work
The value on an unpeeled set is insanely low right now