My suggestion for easy deck building is to stick to 15 card decks. Have some draw more cards cards and focus on having an ultimate hand of no more than 10 cards. The 5 other cards are just filler that either remove themselves from game when used or less powerful cards that you intentionally remove with a card that removes other cards from the game so that your deck size ultimately slims down to no more than 10 so that you can hold all the useful parts parts of your deck in one hand. the draw cards cards are so you can quickly recover your full hand after using multiple cards in a turn.