just my two cents. it all depends when you plan on starting to study. If you plan on starting to study for Step 2 right after Step 1 (and concurrently studying for Shelf exams...)
This is what I did:
Go through Kaplan videos/notes first.. then First Aid (or Step Up if you would like)
USMLERx first (these contain very easy questions that do not reflect the real test, but it tests vital high yield concepts... plus a few of them are actually decent questions.. but only a few).. if you have the time, do this because it hones your mind at the initial step.
UWorld next... this is the big player. no need to elaborate further.
Prior to Shelf exams, use the Pretest qbank. I know these questions are really picky and often very frustrating, but I have to say none of the questions are complete total nonsense. As a matter of fact, it helped me get quite a few # of questions on my Shelf exam.
Kaplan qbank is for if you would like to get psychologically beat up. It did help me answer a few hard pimping questions by my attendings, but do not let the Kaplan qbank be an indicator of how you will do on the real test. Rather, think of it as the supplement that will attempt to help you get those extra few points on the real test... again it is all diminishing returns as you have to do a ton of Kaplan questions to cover the "zebra bases" and you may not see many on the real test of Shelf exams.
hope this helps you.