Tengo ganas de tacos

[Roxerz]

Everything bolded I didn't fully understand which was pretty much everything she said but I think I got the idea. The tengo ganas de, I really don't understand.
I looked up tener + ganas + de and got this:
tener ganas de
to feel like

Also, I think I've heard dar + ganas before, I am not 100% sure but some sort of expression with ganas..

I've never seen antojar but it looks like its in the conjugation format like GUSTAR. I don't know why SE is used but I am currently studying the uses of SE which are reflexivo, indirect, accidental, impersonal, recíproco. I am assuming it is impersonal.

una conversación por whatsapp.

Her: Jaja no se me antojan
Me: jeje pero después el gimnasio debería comer proteína. no cené hoy
Her: Jaja estos cuestan :showoff::showoff: (the muscle emoticon)
Her: Yo tengo ganas de tacos

Her: Those I don't crave
Me: Hehe but after the gym I should eat protein. I didn't eat dinner today
Her: Haha those cost/worth :showoff::showoff:
Her: I feel like (eating???) tacos ???

[Premium]

Her: Jaja no se me antojan
Me: jeje pero después el gimnasio debería comer proteína. no cené hoy
Her: Jaja estos cuestan :showoff::showoff: (the muscle emoticon)
Her: Yo tengo ganas de tacos

Her: Those I don't crave
Me: Hehe but after the gym I should eat protein. I didn't eat dinner today
Her: Haha those cost/worth :showoff::showoff:
Her: I feel like (eating???) tacos ???

The verb is "antojarse". There's no "antojar".

To fancy/to feel like/having a crave.

"Estos cuestan" can be translated as "those are expensive".

I'd say that you translation for "Tengo ganas de tacos" is correct.

[ookami]

Your idea of "tener ganas" is correct.

Tengo ganas de nadar / Quiero nadar = I fell like swimming / I want to swim

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About "Jaja estos cuestan (the muscle emoticon)"

What she is trying to say is that to obtain muscles takes hard work

"Jaja estos -músculos- cuestan (muscle emoticon or her showing muscles)"
"Jaja -to achieve- these takes hard work! (muscle emoticon or her showing muscles)"

[Rusty]

Y ... después del gimnasio ...

[Roxerz]

Y ... después del gimnasio ...

Thanks everyone. In this example, why del? Is it because I am/was leaving a place? I know when I am using the verb salir, I generally use de+el/la. If I use irse to signify I am leaving, does this follow the rule of using de as well?

Ya me voy del gimnasio - Now I'm leaving the gym
Salgo del gimnasio - I leave the gym

[Rusty]

No, it's because 'después de' means 'after' and 'después' means 'afterwards/later' in the marked sentence.
You're newer sentences are correct.