What is the difference between estuve + gerundio and estaba + gerundio ?Feel free to just provide example sentences.

You would use estuve + gerundio only when you've specified the time duration. So you could say: "estuve durmiendo [durante] 8 horas" (I was sleeping for 8 hours), but that would have to be the end of the sentence. It's the same with the normal 'pretérito indefinido': "estuve en la cárcel 3 años" (I was in prison for 3 years).

Estaba + gerundio is used when you're describing the scene or if a length of time hasn't been specified. So, to go by the last sentence used: "estaba durmiendo cuando se cayó" (I was sleeping when he/she/it fell).

Estaba + gerundio is much more commonly used than estuve + gerundio, so I would advise to get used to using it more. However, people will still understand what you're saying anyway because it's a very easy mistake to make.