El dinero y las compras

Rico is rich. Rico is also delicious, and it is the ordinary word for it: está muy rico is said about food several times a day across the Spanish-speaking world.

The two meanings never collide, because ser rico is wealthy and estar rico is tasty. The ser/estar split does the whole job, which is a good demonstration of why that distinction is worth the trouble it costs you.

ganar

Ganar is to earn, to win and to gain. Gano mil euros is I earn a thousand euros. Ganamos is we won. Spanish sees no reason to separate them, and once you notice the connection it is hard to unsee: both are getting something by effort.

Perder is the mirror: to lose money, to lose a match, to miss a train. Perdí el tren is I missed the train, not I lost it.

The question you will actually need

¿Cuánto cuesta? How much does it cost. ¿Cuánto vale? also works and is if anything more common in Spain. ¿Cuánto es? is how much is it, used at the point of paying.

Costar is stem-changing: cuesta, cuestan. It agrees with the thing being bought, not with you, which puts it in the same family as gustar and doler.

cuenta

Cuenta is the bill, a bank account, and a count. La cuenta, por favor is the phrase you will use most. Darse cuenta is to realise, and it is one of those reflexive expressions that has drifted a long way from its parts: literally to give oneself the account.

Shops

Tienda is a shop and also a tent, which sounds like a problem and never is. Mercado is a market. Caja is a box and the till, so pagar en caja is pay at the checkout.

Barato is cheap. It arrives later than it should, because people say the prices of things far more often than they say the word for inexpensive.