Once you have the answer (or at least a ballpark answer), you can do some math to figure out how many cards you need
The most reliable workflow is to scan the front, confirm the set symbol, collector number, language, holo or reverse holo status, and then compare the result against recent market data before deciding whether to sell, grade, or catalog the card
Leafeon ex card 144/131 would be an excellent healer card in play, although anyone who owns this Special Illustration Rare would be encouraged to keep it safe rather than risk it being damaged during a game
Common Card, Played Condition: The cute bug Weedle from Base Set is surprisingly affordable, costing $0.35 for a lightly played version and $0.23 for a heavily played version