yugioh master duel magician of pendulum deck NR PENDULUM MAGICIAN Deck MASTER DUEL

Blasphemous Act (~$0.63) is also a budget favorite and often costs only one red mana to cast

In reality, it reached the limit, but in the now-defunct Yu-Gi-Oh Online, it reached the ban

This card was given out in random packs to participants in the 2019 Pokemon Card Gym Tournament in Japan only for a very limited time, from September - November, 2019

For individual cards and older booster packs and boxes, you will just have to gain a lot of experience and learn the nuances of real Pokemon products and then make educated purchases, ideally with a means of recourse if it turns out you were scammed (some kind of buyer protection program, etc)

Finally, you can Special Summon face-up Pendulum Monsters in your Extra Deck

The land base is another easy way to reduce the cost of Commander decks right now, as so many lands have steadily risen in price over the last few years that if you want to run mostly non-basics, it's going to take up a huge portion of your budget.