Throw down [Counter] cards from the beginning of the game and keep your hand at a moderate number of cards to best take advantage of the Leader effect
You're going to need to buy at least 13 Happy Meals to get the whole set, and that's only if you've got the most fantastic luck, and only THEN if the packs include no repeats and 12.5 different combinations of cards
Like most Magic: The Gathering cards, the value of Soul-Guide Lantern depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Wilds of Eldraine)
Be careful of who you make deals with and who you give resources to, but also dont be afraid to give your opponent a little bit of help if it means you get much farther ahead
We can add photos of the reverse side if you are interested
Whether that's a good thing or not, I'll leave it up to the reader, but having games progress and end in improbable, redundancy-ignoring ways sounds pretty delightful to me