The Original Plan for the Fellowship?

[Inziladun]

If Gandalf had any ultimate ideas for the direction of the Fellowship after Lórien he did not share them with Aragorn.

'I am not Gandalf, and though I have tried to bear his part, I d not know what design or hope he had he had for this hour, if indeed he had any.'

FOTR The Breaking of the Fellowship

It looks like Gandalf really didn't have a definite plan for getting into Mordor, though it seems he would not have wanted the Pass of Cirith Ungol, based upon his reaction to Faramir's news that Frodo was heading there. Gandalf may have had some foresight that somehow Frodo would infiltrate Mordor, but not how he would accomplish it. Gandalf probably would have improvised some plan along the line of what Aragorn proposed, going with Frodo and leaving Aragorn to go with Boromir to Minas Tirith. How that would have played out is impossible to guess, though it's possible that Gandalf's presence would have been detected somehow by the Nazgûl or by Sauron himself, and that could have been disastrous.