"I get shoes from my dad."
Because もらいます already has the received from implied, so you only need に to mark the subject who gave it to you. If you used から it would still make sense but it's important to learn where to put the に with あげます, もらいます, くれます nice and early... it can get confusing!
It marked me wrong when I used から (and used kanji for both nouns). I've reported it.
I think から is more literal as to where in a physical location a subject is located. You're not getting shoes from The Dad who we all know exist at a specific location, it's just your dad.
However, as better explained elsewhere, に pairs up with the verb used in this sentence.
It market me wrong when I typed this (and used the kanji for 靴（くつ）. I've reported it.
The 'に' is interesting here.
That's almost like saying "I receive shoes to my dad" isn't it?
から I imagine is interchangeable here.
I'd have an easier time saying something like
ok yeah, it's longer. But my brain can handle it better xD
The に in a sentence with もらう markes the Person giving. Literally the "from" in "I am receiving shoes from my father".
Your second sentence should be: お父さんは僕にくつをあげる。 Dont forgett the さん. And the thing given by あげる is marked with an を. お父 without the san is not used.
And yes, you have to wrap your head around あげる、くれる and もらう. Took me ages as well. But its necessary to understand all three words.