50-card minimum is for "tournament rules", not regular rules - and makes the game more difficult. If you're having difficulty, ignore this minimum until you can win regularly.
Use a 34-card deck, with a max of 2 of any particular card. This gives you approximately the same ratio of cards/deck as a tournament deck and compensates for the lack of 3x each card in the core set.
If you are struggling, I would just suggest using less cards in your deck. Using decks of about 25 cards with up to 3x each card, you have a lot better chance of winning.