Good recommendations here.
For book-studying, there is Fr Henle’s 1st Year, 2nd Year, 3rd and 4th year Latin. It was originally published in the '40’s and has been reprinted and is readily available. It has a grammar book that goes with it, the same for all 4 years.
A common, or adequate way that can be effective in learning latin to understand what has been said at Mass(by listening; I would also recommend a hand missal) is to go through the 1st year book, doing the exercises assigned, and jumping into Scanolon’s Latin Grammas(1 and 2) reprinted by Tan.
Originally put out after WW2, it was meant for men returning from the war that needed a brush up on their latin before or when they entered seminary. Scanlon’s books contain all the word’s of the Roman Breviary and Missal.
I can say(and I am not the first) that to just jump into Scanlon without having had a previous/more beginner orientated book could be rather tough.
Declensions, verb endings, etc, to learn the language thoroughly, need to be walked through.
Henle, like Collins and other Latin books, can be done on your own, but discipline is key and not much can be accomplished without it. I wish you well in such a worthwhile endeavor. I would just say if there is by-the-book TLM accessible, one does not have to wait to assist at it.
CB