In my 2-player Splendor rules engine, the following actions are possible:
1. Purchase a holding. (90 possible actions, one for each holding)
2. If you do not have 3 reserved cards, reserve a card and take a gold chip if possible. (93 possible actions, one for each holding and one for each deck of facedown cards)
3. If there are 4 chips of the same color in a pile, take 2 chips of that color. (5 possible actions)
4. Take 3 chips of different colors, or 2 chips of different colors if only 2 are available, or 1 chip if only 1 is available. (25 possible actions)
5. If after any action you have at least 11 chips, return 1 chip. (6 possible actions which are never legal at the same time as any other actions)
This still doesn't correctly implement the rules though. In the actual game, you'd be allowed to spend gold chips when you don't need to, which would make purchasing holdings contain extra decisions after you pick which holding to purchase about which chips you'd like to keep.