As Terry said, there are/have been plenty of issues with the Gemini controllers. So not recommended, especially if you are just starting. Hard to tell when something is wrong if you are still figuring out what is right 😀
MC2000 and DDJ-SB are both reliable starter controllers that have plenty of features, imho, for a starting DJ.
Your starting controller should last you between 1 and 2 years if you plan to move ahead, depending on the amount of time you are willing to stick into your new hobby. Too many features are just confusing in the beginning, I think.
The Pioneer and Denon will both have a somewhat decent resell value when you do decide to upgrade in the future.
You can try Mixvibes Cross free without a controller attached, so you can check that out while waiting for the big sale.
And as things stand currently, the only controllers I’d really recommend with Traktor are the NI ones (S2-S4-S8). Traktor is clearly on a path where their software is best suited for their own controllers.
And be sure to check out the review on the new Algoriddim DJ software out for Mac now.
Just my two cents, as usual