If you’ve seen a card you like the look of, or a powerful “cross-combo” (combo cards that feature two Orders on them), you’ll need to build a deck that unlocks that potential.
To play across Orders, you need to equip an Item card that has access to an Element of that Order. Of course, you need to draw that card, so consider putting multiple copies of that Item in your deck. (Remember, the duplicate Item can still be used as combo payment!)
Or, you may want to use the Unaligned card, “Tantosian Blacksmith”, which (if you draw it!) can allow you to search through your deck for an Item card and equip it immediately.