Leone19-
Zero-G is an expensive series to invest in, with all the Synchrom stuff involved. Buying two Beyblades almost becomes a necessity.
But well, the Ultimate Synchrom DX Sets are the best things to start a competitive Zero-G collection.
The Attack and Balance Set gives you a great range of parts, but these are the best ones in there- Gryph, Girago, Balro, SA165.
The Defense and Stamina Set gives you an even greater range of Chrome Wheels, but is quite lacking in good Tracks and Tips. Good stuff- Wyvang, Killerken, Balro, Revizer, E230, 160.
As you see there, you get quite a many amazing Chrome Wheels in either set. You'd only need a Dragooon then, to make it a superb top tier collection. However, you'd need to get certain other beyblades especially for their tracks and tips. BWD, W145, etc are certain parts which are currently quite influential in the meta.
To get a more clear picture of what to get, have a look at the Zero-G Developmental Tier List.
@Ryzr- Buying the Attack and Balance Set is a MUCH better option. Flash is a good thing to have, but almost every Attack Chrome Wheel in the Attack and Balance Set can do whatever Flash does. However, I'd like you to consider your choice between the Attack and Balance Set and the Defense and Stamina Set (I've provided a list of useful parts in each above).
Team IB Revolutions
Thanks to N0body for the avatar and Synth for the signature!