As a recent Flatiron Grad, applying to jobs, networking, and practicing Data Structures & Algorithms are what we do most!
Here are some of my favorite resources:
HackerRank (my favorite at the moment) https://www.hackerrank.com/domains/data-structures
Geeks for Geeks https://www.geeksforgeeks.org/data-structures/
Here is one of the many MANY good Udemy courses: https://www.udemy.com/course/data-structures-and-algorithms-the-complete-guide/ it is regularly $94.99 BUT wait for it, they have sales often!! and you can get it for $10 or sometimes even less on a bundled sale.
And finally, one of the best groups to join for meetups/practice sessions https://www.meetup.com/nyc-coders/events/276218283 NYC Coders hosts a slack channel and a lot of meetups for varying levels, so that is a great group to follow on meetups, and join their meetings and slack server.