Generally agree - in the beginning, we'd recommend starting with easy and progressing to difficult - just to gain familiarity with the question types and gain confidence in navigating through the online test interface.
Once you have a sense of where your strengths and weaknesses are, you can put more attention into your problem areas (i.e. word problems involving rates, number line questions, etc)
After a period of focus on specific areas - then we would recommend mixing questions up.
When you are finished with this online question bank and are looking for additional supplemental questions, take a look at
https://www.gmatpill.com/gmat-practice-test/The questions here are free. If you would like video explanations, a paid membership would be required.
https://www.gmatpill.com