There is no such thing as wasting UWorld. The more times you get through UWorld with solid notes that you review, the higher your score goes. I know a lot of the Carribean students I've worked with used Kaplan questions and Videos and seemed to like it. None of the students at my school or any of my friends at other schools messed with Kaplan, so I really can't say yay or nay to the source.
RX was good, and it fit really well with First Aid- RX is good for reinforcing information you are learning in FA, so it was good to go section by section along with the book. It's supposed to aid in the core concepts, which is different than UW (like OME for step 2).
-UW is where you are going to get the best "bang for your buck". Don't get caught up in your % score, it will go up on its own. Just make sure you are learning while doing questions. Read every question explanation including the answer choice explanation. In all of the studies I've seen, the ONLY resource to positively correlate with a higher score is...UWORLD (Surprise).
I didn't really learn how to study until 3rd year and wish someone sat me down earlier and smacked me over the head with this information.
- Lastly- Don't let these Step 1/Level 1 preparation companies scare you. They make money off of your fear of being inadequate compared to other students. Uworld, FA, Pathoma. If you're a visual learner, then add Picmonic or Sketchy.
-Good luck!