A much harder riddle - Nothing at all

Question

By myself, a long word
Innocent and true
If you scramble me
Dubious is the clue
Again and you will
Regret nothing at all
Once more and
I'm a person who overall
Has nothing to use
Nothing at all

This is a much harder riddle, so feeling generous: here's a mysterious hint...

Not all is as it seems...

Have fun with this one!

Answer 1

Is it the word

Ruse?

By myself, a long word
Innocent and true

Ruse isn't a long word and its a falsehood not true

If you scramble me
Dubious is the clue

If you are SURE you are not dubious

Again and you will
Regret nothing at all

RUES means you regret something

Once more and
I'm a person who overall 
Has nothing to use 
Nothing at all

Not sure about this one but I think its the last anagram of ruse, USER. If you are a user you are a person who is using something

So

This whole riddle is a RUSE