Einstein MS

Initial Release: Winter 2003,  Fukubako 2004 Prize Beyblade (Lime-Green, Secret Light-Blue)

Additional Releases: Hasbro's "Hopper MS" Starter (Lime-Green), Random Booster ACT2 (Fuschia), Event Limited (WHF Dark Green), Corocoro Limited Lucky Box (Gold)

Bit Protector - "Small Type"

Should be noted that BP Size Type on initial release is not consistent for every cycle of production or re-release. Being reproduced the following year could mean a  different BP Size Type for a given Beyblade.

Attack Ring (AR)

Metal Spring, ~16g.

Best Possible Combo:

AR: Metal Spring (Either spin)

WD: CWD Reverse Defenser (with Metal CWD found in RBA2)

RC: Bearing Core 2

or

AR: Metal Spring (Either spin)

WD: CWD God Ring (with Metal CWD found in RBA2)

RC: Metal Change Core

Game Plan: I've provided two combos for Metal Spring, not because I like Metal Spring or that it is incredibly versatile. Instead, it is because not only do I feel bad for it, but you may as well try it out in all of its glory if you intend to use Metal Spring. The first combo works almost passably because Metal Spring is so small, and the CWD can bear the onslaught of Attack type aggression quite well on its own. The second one is a Compact that is unique but equally dubious in providing decent performance, mostly something to try out of novelty.

Weight Disk (WD)

Circle Heavy

CWD Free Defense Ring, ~20g.

Best Possible Combo:

AR: Metal Upper

WD: CWD Free Defense Ring (with Metal CWD found in RBA2)

RC: Grip Flat Core (Ultimate Version)

Game Plan: Knock things out, it is that simple. Metal Upper was missing just a bit of secret sauce to make it stand out, because on its own it was a bit lacking compared to The Big Three. CWD Free Defense Ring is that secret sauce, giving it just the nudge it needs to be a powerhouse against an overwhelming majority of what can be thrown at it from the HMS series.

Circle Heavy, in regular Einstein MS releases

CWD Free Defense Ring (RBA2). Courtesy of @DerexGT

Running Core (RC)

Spring Core, ~2g.

Best Possible Combo

AR: Samurai Upper (Same-Spin)

WD: CWD Defense Ring (with Metal CWD found in RBA2)

RC: Spring Core

Game Plan: Using this Stamina combo means you expect to only face Stamina and Defense combos. In most any matchup you can be knocked out, this includes against Bearing Core and Bearing Core 2 combos. Needless to say, Attackers will knock this combo out before you can blink. Because you are aiming to be in the same spin direction as your opponent, weak launching is not on the table. In same spin its ability to destabilize is incredibly powerful and will allow it to out-spin any other combo provided it stays in the stadium. It is as simple as that. Strategize or predict the spin direction of your opponent, launch flatly, and try not to get knocked out. 

Provided by @BladerKei, creator of BeyBase.