I actually think the +5 Deck Size is the greater cost associated with Versatile than the experience because its going to make it harder to find and draw your key assets - weapons to fight with, tools to gather clues with, etc
On to the best free cards
The average pack does not exist in reality and has a chance of becoming a God Pack or a Regular Pack upon opening
Doppelwarrior takes it further, enabling plays like: Librarian + Formula = draw 2, then Synchro during your opponent's Main Arcanite, to wall up with 2400 ATK, and pop 2 cards on the crackback Black Rose, to nuke their board at the end of their Main Phase Debris + Dandy + Doppel = 2-card Trishula Formula into Librarian Librarian Formula = Draw 5 Quasar All seems well until you realize there is a lot of hate that the deck is suceptible to, ranging from pinpoint disruption or devastating floodgates
Zopandrel, Hunger Dominus Zopandrel, Hunger Dominus is a perfectly fine card, one that can dish out tons of extra damage in a green stompy deck
eBay may be the most familiar to many, but its definitely not the cheapest place to find cards to flip