I collect theme decks, 1 of 2 theme decks per set. I usually collect the one where the theme deck mascot picture is to the right of the Active Pokemon on the playmat. I also collect the theme deck that is the same as the starter I picked in the games. The starter that I pick in the game is the starter that the female player character chose in a canonical storyline such as the anime, or perhaps from Pokemon Adventures, which is usually the weaker starter of the male protagonist. I started from Undaunted, worked my way back to Platinum Supreme Victors while working my way forward to the current set. So from Supereme Victors,
Overflow
Flamemaster
Growth Clash (I picked Chikorita in SoulSilver, and the picture of Meganium is to the right side of the active pokemon)
Steel Sentinel
Nightfall
Royal Guard
Recon
Red Frenzy
(Hard to explain, but for the first version, I always pick the male character, while in the second version, I pick female. I use the male protagonist to fit the basis of the starter pokemon and what his "friends" chose, and try to match it with the anime. Cilan is supposed to be the "leader" of the brothers, and it makes sense that the male player's starter should be oshawott, which means in the games, you face him. The female player's starter should be the one weaker. Bianca's anime starter is Tepig, and if the male player's character is Oshawott, it is like that in the game. Also, Trip's starter is snivy, similar to Cheren, who seem to both want power. After figuring that out, and that the male character picks oshawott to fit with the anime, then for the other version, I pick the female character and the pokemon weaker than what the male picked. That is, tepig. Then Cheren's pokemon would be Oshawott, and Bianca's pokemon would be snivy, which doesn't match the anime, and it doesn't matter because I match the pokemon they would have had in the anime, where Cheren = Trip, if I picked black version with the male character, and not white version and the female character. Due to shortage of cash, I always play the second version, so I always pick the girl. It's only a game sprite, and besides too many people already pick the dude anyway so I pick the least picked gender, if you know what I'm sayin'.)
Continuing on
Power Play
Furious Knights
Voltage Vortex
Shadows
DragonSnarl
I also collect tins. I am very specific as to what tin I collect. The tins I collect MUST be the group of 3 tins that TPCi releases twice a year, except with the case of 2008 where they release 2 sets of 2 tins in a span of a few months, but that doesn't really matter, since I am probably not going to buy super old tins, or any tin before the start of 2011. I started collecting tins in the beginning of 2011 with the Black and White sneak Peak tins. My rule is this. I already explained this. Of the 3 tins, I must buy ONLY 1 of the 3. I must never by standalone tins such as the V for Victini tin, or tins that come in pairs, fall 2008 notwithstanding, such as the Reshiram and Zekrom tin they released mid 2011. The tin must fit the theme of the starter I chose and the theme deck mascot. I have the Tepig tin, Emboar tin, and Zekrom tin. I also made a tentative tin that my brother, who is tentatively supposed to own pokemon black, and pick the dude character, and start with Oshawott, will use the "other" theme deck, and thus have tins based off Oshawott and the "other" theme decks. I had a hard time picking between Mewtwo EX and Darkrai EX. I would have bought him Oshawott, Samurott, Reshiram EX and Rayquaza (fits with Garchomp from Dragonspeed theme deck, because that in turn fits with the Japanese set Dragonblade). I then tried to find something in common with the prior 3 tins that I already own in order to pick Darkrai over Mewtwo. I look at the side of the tin to see pictures of the 3 pokemon that are supposed to be the 3 tin mascots. I also look at the order in which the black star promos are numbered, which for 2011 and onwards seem to have the same order when you look at the 3 pokemon while turning the tin clockwise. For example, if I have BW01 promo, my brother would have BW02. If I have BW03, my brother would have BW01. Right now, I have BW02, my brother (doesn't have) BW03, which is the one he was supposed to get. When I said that my brother was supposed to have tins, he isn't supposed to, and he isn't interested nor am I buying tins for him. I use it as a marker to decide which tins I pick, so Rayquaza is BW47, which fits the "other deck" dragonspeed, while I have dragonsnarl. I look at the picture of rayquaza on the side of the tin, and rotate the tin counterclockwise until I see the next pokemon. Darkrai. It is also that Darkrai is BW46, one less than BW47. In the case of Reshiram EX and Zekrom EX, the same trick is used. Reshiram EX fits the Explosive Edge deck. I look at Reshiram EX's BW black star promo number, see that it is BW36, but find that BW35 isn't a tin promo, so I cycle back to BW38 for Zekrom EX tin, which also fits the Voltage Vortex deck I own. Same with the previous 2 sets of tins with the starter pokemon.
This trick doesn't necessarily work. The Spring 2008 and Spring 2009 tins has it so that the I have to rotate the tin clockwise from my brother's tentative tin, rather than the usual counterclockwise. So far this worked from Fall 2009 and onwards. If I were to tentatively get older tins from Fall 2009 onwards, I would get Charizard, while my brother gets Garchomp, because a picture of Charizard is shown in the overflow deck playmat, while a picture is shown in the ignition deck playmat, to the opposite side of Milotic and Arcanine respectively. I would have picked meganium, while my brother chooses Typhlosion. I would pick Raikou, while my brother picks Entei. The rule discussed above works with these tins, but this rule is uncertain if it is going to ensure it matches the theme deck I use as well as matching the other theme deck. Unfortunately, rotating the tin is backwards, while looking at the number for the HGSS promos is forwards.
Nowadays, I don't buy tins unless they are cheap. I changed my habit to collecting all theme decks rather than 1 of 2. But sometimes I am suckered into buying tins, because I need to store my cards. Tins to me are a better investment than box sets. The reason why I don't collect all 3 is because I also (try to) collect Magic Fat packs, and Yugioh tins. It takes up way too much space in my room.
Here's a link to their tin page 
