is there difference if i said “is it worth it to buy/buying it” and “is it worth to buy/buying it”

Neither sounds very natural. You might say: - “Is buying ___ worth it?” - “Is ___ worth buying?” - “Is it worth buying ____?”

This one is not a thing : Is it worth to buy

I would say "Is it worth it?" Or "Is it worth buying?" Alternatively, you could say something like "Is the price worth it?"