First off let me say the Grobo on its own is incredible and very capable machine. That said, modding in my opinion is half the fun . A little while back a bad ass grower called @Hellyesshedid put together a very comprehensive list of all of the items and modifications one would want to consider when growing with Grobo. You can check it out here:
The only things I would add as a must is a quality external air pump.
Should your Grobo be prone to internal temperatures above 75 or if you have a desire to diminish the wonderful smell that your plants emit into your home, you may want to consider a heat extraction/smell blocking system you can check out a couple options here from myself and a fellow Grobo grower @KeefGreenLeef (tip: he will actually build one and send it to you )
All in all, you’re going to have a blast with this process, it’s fun as hell and very easy to become obsessed. Also as a side bonus, you’re going to end up with some very buds welcome to the Grobo fam, we look forward to growing with you!