Is there an English equivalent for this Tamil proverb - "A painting of a bottle gourd is worthless while preparing stew"?

Here's one that highlights the problem with relying only on the theoretical at the expense of the practical:

In theory there is no difference between theory and practice. But in practice there is. - reported by Walter J. Savitch, originator unknown but possibly Jan van de Snepscheut according to snopes.com

(Thanks to @DCShannon for the snopes link for attribution.)

"The map is not the territory" is a common expression, especially among military veterans.

There is a specific example of a well-known snowclone, by Ernst F. Schumacher:

An ounce of practice is generally worth more than a ton of theory.

Apart from the weight metaphor, though, it's disappointingly mundane. I'd prefer it if the bottlegourd / stew saying caught on.

Experience is the best teacher

You will learn more from things that happen to you in real life than you will from hearing about or studying things that happen to other people.

Nothing beats experience has been used for at least 50 years. Surprisingly, Google ngrams doesn't show any occurrence before year 1965.