I am bored so here's some quick trivia. Will be updated constantly.
SEASON 1
Booster Set 1: Well the first booster set for this game! Obviously that is a start. Also the only booster set to include a RR trigger (Future Knight Liew). It is the first set to have an SP with alt artwork. The only booster set to have triggers previously printed on the two trial decks. (TD01 and 02)
Booster Set 2: The first booster set to introduce single clanning.Also the first JPN booster to include deck dividers on first print. (Thanks those who contributed to this)
Booster Set 3: The first "evil" based set. Also the only set that has the super consistent ride chain mechanic.
Booster Set 4: The only set to introduce a ride chain that when you ride the specified grade 1 you get a definite grade 2. It is also the second main booster set to have an SP with alt artwork.
Booster Set 5: The first booster set to introduce the crossride mechanic. Also the only booster set to have a foil starter (Wingal Brave) besides Booster Set 1.
Extra Booster 1: Basically, the first extra booster! It fills up on cards used in the comics. Also the first 11k to have a different type of negative drawback (Instead of clan, it is archtype).
Extra Booster 2: The first booster set ever to introduce a 1 clan only policy.
SEASON 2
Booster Set 6: The first ever 102 card booster set. Also the first booster set to introduce Limit Break.
Booster Set 7: The only booster set to surprise everyone by introducing builds that were previously not viable/usable to become extremely viable builds (CoCo and Great nature)
Booster Set 8: The first main booster set that has an 11k that does not follow the limits of other 11ks (Dungaree). Also the first set to have a single crossride unit.
Booster Set 9: The booster set with the most number of crossride units. Also the only booster set that reprints perfect guards in the same season (Mark and Guld) It is the first booster set to feature the dual clan mechanic. Also it is the only set that gives only 1 card to 2 specific clans (RP and SP) Also, the first main Booster to have all Grade 3s in the RRR slots, and all 11ks have a new drawback effect called Lord.
Extra Booster 3: The first extra booster to have Limit Break. Also the first booster set to introduce a second 10k vanilla for 3 clans. (RP,SP and Kagero)
Extra Boosters 4and5: The second sets that are 1 clan only. Also the only booster sets to be released together on the same date.
SEASON 3:
Booster Set 10: The booster set with the most number of Perfect Guard prints. It is the second set to ever reprint a perfect guard. Also it is the first booster set to introduce a second archtype based perfect guard for 3 clans. (GP, RP and Narukami)
Booster Set 11: The second booster set with only 1 crossride unit (This is yet to be confirmed)
Extra Booster 6: The first booster to feature a clan that is boosted in another 1 clan only booster. Also the only Extra Booster with a Crossride unit (This is yet to be confirmed)