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>And lastly, what the best niche idea today?

I'm not sure anyone will will reveal their best niche idea. ;)

Google Makes AdSense Approvals Faster and Easier [webmasterworld.com]

I got adsense account 4 years ago for some reason it got banned.

Unfortunately AdSense does not believe in second chances. If your account was banned, that's the end of having an AdSense account.

Yep; once banned and appeal(s) failed its over for ever. To get another account is tantamount to fraud.

not really sure why

Cold-blooded comment: You're much more likely to get useful information if you don't begin by insulting the reader's intelligence.

Analogous scenario that comes to mind: Person gets banned from a php/bb forum. (I use this name because I'm familiar with how they work, and because it isn't the package used by the present forum.) When this happens, attempts to log in are met with a message saying "You've been banned and here's why". The next step is invariably an email to the forum administrator saying "I don't know what's going on, I somehow can't seem to log in." Every ### time.

What did you do, and what steps have you taken to ensure that you won't do it again?

So how long does it take to get another adsense account?
Would you recommend to create a blogspot account (becuase that's where i got my adsense before) or should i buy a domain/hosting a create a new blog site?
Should i use a new gmail and new physical address?

You are not listening to what you are being told. you are NOT allowed another account.