Can I buy action points?

You can't really.... Check the cash bought bundles in the shop, sometimes Action Point potions are pack of a package there, but if I remember rightly, you don't get many.

The best way is to get more Action Point potions via the VIP store. There are a bunch for sale weekly and can be bought using food. You can also get some potions sometimes when your alliance defeats a fort, and also as alliance rewards for some premium packs.

Look out for the increased action point recovery rune, and utilise commanders that use like Action Points for tasks.

When you run out of AP and have used up all of your potions you will get an offer to purchase 500 AP for gems, you can do this a number of times, but each time you do, the price of the 500 AP increases.

This resets daily.