I agree with Michael...take all the time necessary to get that machine perfectly level and square before you even think about running it. It will make a "yuge" difference in performance and reduce the number of "little frustrations" that will get in the way of what is already an impressive learning curve for a new-to-CNC user. This is really one of the single "downsides" to a modular machine but with care, it's not a mountain, only a tiny rise to climb before you start making a mess.
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The most expensive tool is the one you buy "cheaply" and often...