Sponsorship process information required for visa

Hi, I have a few options to show as a sponsor but in all cases, I don’t know what exactly I need:
1. Can I show my own bank statement as self-sponsored? If yes, what exactly do I need to show other than my bank statement? And, how much amount should be in my bank?
2. If I show my parents as sponsors, how much minimum amount should they have in the bank? and what other documents will I require? (Proof of income, affidavit etc)
3. If I show my uncle’s bank statement who is a German citizen, will his bank statement and informal sponsor letter be enough (signed by him)? Or is it absolutely necessary to provide a formal obligation letter?