The Quality of GMAT Club quant CAT'S are really good. You don'the need any other material to supplement the tests apart from the Quant CAT'S provided.
I used to give 1 Quant tests daily before my actual GMAT, it helped me a lot to Ace the test.
Also, The explanations provided by bunel is really good. The quality should be rated 5 stars. I used to refer to the explanations even when i got a question correct , in order to check if there is a shorter approach available to answer the same.
I started With a Q45 intially and ended up getting Q 48 In my real GMAT.