Intro to symbolic logic, for sure. There, you should learn argument structures and other things like that. The Critical thinking class will only be marginally beneficial.

Meh, I'd say elementary logic will be much more on point, although symbolic will give you good practice and force you to make the elementary syllogism stuff, like what's on the LSAT, second nature (which is what you want on a timed test). My person anecdote: at out school, we needed only 4 philosophy classes to get a minor. I took Logic, Symbolic Logic, Existentialism, and the Philosophy of Aesthetics. My GPA over those 4 classes was a lot higher than my "background" GPA, primarily because I really enjoyed those classes.

So, I'd say this would be the best plan: take Elementary logic.
If you like it and do well in it, take symbolic.
If you like that and do well in it, keep taking philosophy classes.

TITCR.

By far the best way you can possibly ensure a good score on the LSAT is simply to study the LSAT itself by taking timed practice tests. IMO you should take philosophy courses if it will interest you and improve your GPA, but courses in philosophy or formal logic are not necessary to do well on the LSAT