If you consider to buy a real rubik cube - and I suggest you to do this! - then here's my advise:
Buy a speed cube! Don't buy the 80ers original one. They don't rotate well, it will get on your nerves.
Buy a 5,5 * 5,5 cm cube, don't buy the original cube which is 6,Xcm.
Don't buy on amazon (never)!
If you have time to wait 3 weeks for shipping you can get really good speed cubes for 1€ directly from china.
Ebay is the best place to get a cheap one.
I got two of those: https://www.ebay.de/itm/Magic-Cube-3x3x3-Super-Smooth-Fast-Speed-Puzzle-Kids-Toy-SDL2-/232897758193?nordt=true&orig_cvip=true&rt=nc&_trksid=p2047675.m43663.l10137
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