You want a mechanical keyboard and mouse bundle that will survive years of heavy typing and late-night gaming sessions. Buying a solid set right the first time means you aren't replacing cheap switches or sticky buttons in twelve months.
Big holiday sale events are the right time to buy because manufacturers drop prices to clear out inventory. Look for last year's model on discount since the newer version usually just adds cosmetic lights without changing the actual switches or sensors.
Remember that the 0% intro APR for 15 months on purchases and balance transfers is a hard deadline, not free money. If you still have a balance left when those 15 months are up, the standard interest rate kicks in on the whole original amount.