You don't need a collection. You need one stone. The right one for right now.
Here's how I tell people to choose: don't research it first. Go to where the crystals are and pick up the one you're drawn to. Or choose from an image online based on which one you keep returning to. That pull is already your intuition working.
For beginners, the five I recommend most: Clear Quartz (amplifies clarity and intention), Rose Quartz (self-love and gentleness, for women being hard on themselves), Amethyst (calm and anxiety reduction), Black Tourmaline or Onyx (protection and grounding, good for anyone who absorbs other people's energy), and Moonstone (intuition, cycles, inner knowing).
Once you have your stone, the practice is simple: hold it consciously. Five minutes in the morning. During a difficult call. The stone isn't doing anything complicated. It's giving your nervous system a physical anchor for the intention you've already set.
The Crystal Starter Kit is where I'd start. Everything to begin with. Nothing unnecessary.