Probably or probally but never prolly. Only seen that used few times online.

Probly - I don't pronounce the "a".

How do you pronounce *comfortable*?

I don't know how it sounds like, but I'm guessing it's something along the lines of "probely"

I avoid the stumbling over those Bs. I say "most likely"

With the following syllables:
pro - ba - bly

phonetic:
[prob-uh-blee]
/ˈprɒbəblɪ/
http://www.dictionary.com/browse/probably?r=75&src=ref&ch=dic
(click sound icon)

prob·a·bly \ˈprä-bə-blē, ˈprä(b)-blē\
https://www.merriam-webster.com/dictionary/probably
Funny, this one goes for the 'ah' instead of 'uh' sound.

Pro-be-bli

"Probly" lol

Most people round here say is as "probly". We don't have a problem with saying the letter "b" so we don't say "prolly" here.

prob-ber-ly