what is the difference?
I think, both 'yo estoy interesado en~' and 'me interesa en~' patterns means 'I'm interested in~'.
if there is a difference between them, what is it?

and 'me gustaria ~' ,'me encantaria~'? is there a difference?

I really wonder.

Question

what is the difference?
I think, both 'yo estoy interesado en~' and 'me interesa en~' patterns means 'I'm interested in~'.
if there is a difference between them, what is it?

and 'me gustaria ~' ,'me encantaria~'? is there a difference?

I really wonder.

Answer

"Yo estoy interesado en" indeed means "I'm interested in". If you use "me interesa" there's no need to use the preposition "en". E.g.:
- Estoy interesado en el arte contemporáneo.
- Me interesa el arte contemporáneo.
As far as I know, here in Spain "me interesa + noun" is much more common than "estoy interesado en". It's not exactly wrong, but it sounds like a literal translation from English.

"Me gustaría" and "me encantaría" can be used for more or less the same thing, but "me encantaría" is stronger.
- Me gustaría ir a la playa. (I'd like to go to the beach)
- Me encantaría ir a la playa. (I'd LOVE to go to the beach)

Hope it helps!