Looking for help, not an answer

As the title says: I'm looking for help in how to go about breaking this cipher, not an answer for to the cipher. I have been given a cipher that I am having trouble identifying. I'm not looking for you brilliant beetles to solve it, more I'd like some help in how to solve it. To that end, I will describe it, but not post it, if that's alright.

It seems to be repeating the same three numbers in varying combinations. I suspect each combination represents a letter because the number combos themselves repeat.

For example the first line reads: 9 22 • 22 • 24 22 9 9 9 • 22 • 24 9 • 24 24 • 9 • 24 24 22 • 24 9 9 • 24 22 • 24 22 9 9 9 • 24 9 • 22 • 24 9 22 • 24 24 • 9 22 • 24 22 • 24 24 • 9 9 9

I have been given a keyword. At first I thought it was a Polybius, but the grid isn't large enough and then I looked at a Trifib, but that didn't seem to work.

Any thoughts?