I have gone through Wheelock’s and have translated Cicero’s first speech against Catiline with help from Maclardy’s Completely Parsed Cicero. Are there any more advanced textbooks I can go through to expand my Latin? I am interested in exploring poetry (Virgil, Ovid) or prose (J. Caesar, Livy) but haven’t been able to find many resources except for Latin “readers” like Maclardy’s.
I’d suggest plunging into some Latin prose, such as Caesar or Cicero, using one of the annotated editions aimed at high-school students, but not one that parses everything for you (though you may find parsing on your own a helpful learning procedure). There are many such editions from the late 19th/early 20th centuries available used at very modest prices. I think American Book Company or Ginn used to publish solid texts with commentaries. The Cambridge Greek and Latin Classics series (“green and yellow”) are very good, but might assume a somewhat higher level of language skill than you have reached–although they will provide much more up-to-date background information. You might try using both types of commentaries But if you’ve gone through Wheelock, you should have all the grammar you need.
Wheelock has its own follow up reader which may interest you. Some like to use Orberg’s Lingua Latina series as a way to quickly build vocabulary and reading speed after a book like Wheelock. You might also like some of Geoffrey Steadman’s readers available at https://geoffreysteadman.com/. Clyde Pharr wrote a heavily glossed edition of the first several books of Virgil’s Aeneid.
If you want something that is specifically not a reader, then a reference grammar such as Gildersleeve may be to your liking. Composition books were also traditional follow ups to a primary textbook and hit the finer parts of grammar and syntax. There are several available from textkit. Bradley’s Arnold (see http://bmcr.brynmawr.edu/2006/2006-06-26.html) is considered by many to be one that will take you far, albeit harder than some of the others.
Bolchazy-Carducci has a good series as well, just entitled A _________ Workbook, available for Caesar, Vergil, Ovid, Catullus, Horace and Cicero. You can get a student and teacher edition. They run about $27 each. They are designed to help prepare for the College Board AP Exam. Here’s the publisher’s web address: www.bolchazy.com
I would recommend this 1907 edition of De Bello Gallico: fully macronised, with plenty of vocabulary, grammar and historical notes, and an extensive grammar appendix with references to the text.