Considering that Ecclesiastical Latin stems from the Classical language it doesn't seem contradictory to start with the latter, although I have heard (I cannot confirm this to be true or not) that the Classical language is harder to learn.

You might be interested in Henle's book series. He teaches both Classical and Ecclesiastical. Learning Classical will give you a foundation to read plenty of good material. Seneca for example.

The problem with Classical Latin …. Ecclesiastical pronunciation all the way for me.

How different is Ecclesiastical Latin from Classical Latin?

Lets say I wanted to use Rosetta Stone's Latin program . . .

No one so far has mentioned something of overriding importance: that s2srea is interested in learning Latin so as "to be proficient enough to read through the Missale Romanum." But to read the Missal, he needs to learn ecclesiastical Latin, which is a species of Late Latin and thus is enormously different from classical Latin in syntax, mechanics, and vocabulary. Thus, he will need to learn not only the classical structure and vocabulary of Latin but also the myriad ways in which ecclesiastical Latin departs from them. This is a task far more easily said than done. …

… the actual word order within … any sentence depends upon the relative importance in the sentence's context of giver, recipient, and thing given, the rule being that the last word in a sentence normally is the most important one, the next most important being the first word, with subsequent words before the last one being of progressively less importance. (That is, while it is certainly true that Latin is at root a synthetic language, in the terminology of linguistics, it is not one where word order counts for nothing. Quite the contrary.) This rule of classical Latin and a great many other rules go out the window when one is talking about ecclesiastical Latin, however. Or to be tediously accurate, sometimes it goes out the window and sometimes it doesn't. That is the crux of the problem it presents to the student of classical Latin. …

… The finest Latin scholar I ever knew, a long dead former college teacher of mine, told me that since he had studied ecclesiastical Latin for only four years, he never trusted his own translations of Church docuмents. (The point is that he could read Cicero, Caesar, Tacitus, Virgil, Horace, Catullus, and even Ovid as fluently as most commenters here could read a third-grade primer.) Of course, s2srea won't be looking to cross swords with docuмentary scholars, but if he studies only classical Latin, he will frequently find himself wondering why the Missal's word choices and constructions seem so odd, if not plain dumb.

It's very different. But why haven't you referred to your own thread from this past June (Latin/General Discussion)? You got a great many responses there, including this one from me (excerpted):

Quote from: Vladimir

Considering that Ecclesiastical Latin stems from the Classical language it doesn't seem contradictory to start with the latter, although I have heard (I cannot confirm this to be true or not) that the Classical language is harder to learn.

Ecclesiastical Latin is far harder to learn. Classical Latin is a dead language. All of its structures and conventions are known, and they will never change again. Ecclesiastical Latin is anything but dead, however, and like any other living language it has changed in more ways than I am qualified to count since the death of vernacular Latin, which was already several centuries into its "late" phase by Justinian's time, when Greek supersession of Latin as the empire's official language was beginning.