After years of experience with Russian, I'd say that the language's verbs of motion are probably the most challenging aspect for English speakers. Beyond whatever your class is using, you'll need a workbook dedicated specifically for motion verbs and you'll need to do hundreds of exercises before they can sink in.
I'd recommend Murav'eva's Verbs of Motion in Russia
, cheap used copies of which are easily available at Amazon.com. When I started researching verbs of motion in Russia's minority languages and needed to understand the Russian system first to use various works of scholarship, I'd always start my day with a few exercises from her book.