What's a sensible order to learn the three techniques?

Major System → number PAO → memory palace → drill decks/numbers, in that build-up.

A workable path:

1. Major System first — it seeds your number images (and Persons).
2. Number (or card) PAO — build and drill your composites.
3. Memory palace — routes to store the composites in order.
4. Integrate — memorise decks and long numbers, slow then fast.

Each stage stands on the previous one, which is why courses teach them in roughly this sequence rather than all at once.

Go deeper:

• Nelson Dellis — The Major System — step 1: learn the Major System first.
• Nelson Dellis — How to create a 2-digit PAO system — step 2: build and drill a number PAO.