While a quick solution for Crowns is an interesting idea, it sounds as though you aren't using Companion Tasks to help your pirate keep your crew trained. Your entire crew isn't needed for battle, and can be assigned to these tasks instead.

Keel Hauling is available for those companions who match your pirate's level (or are higher than) -- send them to get free tomes.

Scavenging and Plundering with companions can get you gold, or gear you can sell for gold, to buy tomes with.

Pet wrangling can provide you with pet snacks, pet gear, and even eggs, which you can use or sell for gold.

Another way for fairly quick gold, depending on your pirate's level, is to do the Ambassador's quests on the party barge every day -- if you are over level 51, it only takes about 15-20 minutes and you'll get 10,000 from each Ambassador. Mid-level pirates have to fight striped bumabloons for the Marleybone Ambassador, so that one is a pain, but even if you only did the other three, you get 5,000 gold each (between level 21 and 50). 40,000 gold per day buys a lot of tomes.

Omg YES for pet levels!

And an elixir that just maxed out a single pets Power after you'd trained it to whatever max age level is (super?)