Hi L.,
The 2nd foods don't have any chunks in them, so you can move on to them at any time. Since a lot of them have mixed flavors (like Apple Banana or whatever), just make sure your daughter has at least had one of the flavors before, all by itself. That way, if she has an allergic reaction, you will know which flavor is the culprit!
The 3rd foods definitely have chunks in them (well, MOST of them, anyway.) I can't remember exactly when I started feeding my son the 3rd foods, but I do think it was about 9 months, MAYBE 8. All it is, is trial and error. You would give her a bite and see how she handles it. If she starts to gag or just doesn't seem to like it, just hold off for a while and then try it again. You will see that some of the 3rd foods vary in how chunky they are. I pretty much stuck with one brand (Gerber),but one flavor would be more chunky than another flavor.
Good luck!