A good custom mechanical keyboard is something you buy once to use for five to ten years. If you plan your build right the first time, you avoid buying a cheap board now only to replace everything six months later.
Group buys and limited keycap drops run on tight schedules, but grabbing in-stock extras or last year's board design often gets you the same quality for less wait. If you use a card like the Discover it® Cash Back, you can secure your parts today and spread the cost out over time without paying extra in interest.
Keep in mind that a 0% APR window is a hard deadline, not free money. If you still have a balance on the Discover it® Cash Back after 15 months, the regular interest rate kicks in on whatever is left, making your keyboard build a lot more expensive.