Current meta - How well the deck prepares you for competitive games, and whether it teaches you about newer mechanics
Do it enough times and youll eventually have enough cards to tool around with making your own decks to try out in the games friendly mode, Quick Start
Add in the absolute monstrosity that is Sliver Legion, granting a major +1/+1 bonus to all the Slivers on all sides of the battlefield, and you will have a truly frightening army of faceless monsters

September 1, 2030) Sephiroth (Blue/Black) Creatures(21) 3 Al Bhed Salvagers 3 Il Mheg Pixie 1 Sahagin 1 Sephiroth, Planet's Heir 1 Seymour Flux 3 Shambling Cie'th 3 Shinra Reinforcements 1 Ultimecia, Temporal Threat 4 Undercity Dire Rat 1 Xande, Dark Mage Sorceries(6) 1 Deadly Embrace 2 Evil Reawakened 1 Relm's Sketching 2 Retrieve the Esper Instants(7) 2 Dreams of Laguna 2 Overkill 3 Sephiroth's Intervention Artifacts(1) 1 Magitek Scythe Lands(25) 9 Island 12 Swamp 4 Treno, Dark City Cloud (Red/White) Creatures(19) 1 Adelbert Steiner 1 Barret Wallace 1 Beatrix, Loyal General 2 Cloudbound Moogle 1 Cloud, Planet's Champion 2 Coeurl 4 Dwarven Castle Guard 1 Freya Crescent 1 G'raha Tia 3 Item Shopkeep 1 Lightning, Security Sergeant 1 Rosa, Resolute White Mage Sorceries(2) 1 Suplex 1 The Crystal's Chosen Instants(5) 2 Fate of the Sun-Cryst 1 Judgment Bolt 2 Slash of Light Artifacts(9) 1 Dragoon's Lance 2 Samurai's Katana 1 Ultima Weapon 2 Warrior's Sword 2 White Auracite 1 White Mage's Staff Lands(25) 8 Mountain 13 Plains 4 Rabanastre, Royal City

That's right
It can pick off most creatures and proliferate while it's at it