With the Battle Arena Decks out and in full swing, I will first be providing coverage of some decks that can be made by purchasing two copies of this product; subsequently, this post will be updated with a "double-deck" made from a single product which contains two different decks. (Note that the contents of this post are for the Expanded 2016-2017 format of Black and White-onwards, unless otherwise noted.) As was the case with the Darkrai and Mewtwo Battle Arena Decks, even if you do not play Expanded, this deck contains many useful cards for the Standard (Primal Clash-onwards) format. The purchase is made better if there are people in your area you can trade with that do play such a format, and would thus be interested in trading for cards you might not use.
[Expanded]
Pokémon: 15
4 Rayquaza-EX
4 Eelektrik
4 Tynamo
1 Raichu
1 Pikachu
1 Keldeo-EX
Trainers: 31
4 Professor Sycamore
4 N
2 Professor Birch's Observations
2 Lysandre
2 Skyla
1 Karen
4 VS Seeker
3 Ultra Ball
4 Level Ball
1 Float Stone
1 Professor's Letter
3 Skyarrow Bridge
Energy: 14
4 Fire
10 Lightning
Strategy: The strategy of this deck is rather narrowly focused, but strong if left unstopped. Eelectrik's Ability, which can be used once per Eelectrik in play per turn, allows for a Lightning Energy card to be attached to a Benched Pokemon. Rayquaza-EX should use its second attack, discarding all Lightning Energy, leaving it with one Fire Energy attached. Using Skyarrow Bridge to retreat for free (or Keldeo-EX and Float Stone if Skyarrow Bridge cannot be found to enter play, or to remove the Asleep or Paralyzed Status Conditions) allows an Active Rayquaza-EX to switch with a Benched Rayquaza-EX. Eelektrik can power up whichever Rayquaza-EX is on the Bench for another powerful attack, doing up to 240 damage per turn. While very strong, this strategy is vulnerable to Ability-lock cards, such as Hex Maniac, which significantly reduce how quickly Energy can be attached. Room for improvement would involve trading for Raikou, both the non-EX (1) and EX (2) variants, to replace the Raichu line and one Rayquaza-EX, in addition to the Ace Spec card Computer Search.
[Standard]
Pokémon: 16
4 Raichu
4 Pikachu
2 Articuno
2 Regice
2 Octillery
2 Remoraid
Trainers: 32
4 Professor Sycamore
4 N
2 Lysandre
1 Fisherman
1 Skyla
1 Karen
4 VS Seeker
4 Ultra Ball
4 Level Ball and/or Dive Ball
2 Professor's Letter
2 Switch and/or Escape Rope
3 Rough Seas
Energy: 12
12 Water
Strategy: Not fantastic, but functional. Raichu focuses as the primary attacker (using its first attack, due to a lack of Lightning Energy), with Regice and Articuno providing backup support. By finishing an opponent off with Articuno's second attack, you can claim an often-unexpected extra Prize card, thanks to its Ancient Trait.