A good external solid state drive backs up huge video files and runs games without stuttering. You want something built with a rugged metal case that handles drops, because buying a cheap plastic one now means replacing it in a year.
Wait for major retail deal events like October sales or Black Friday to pull the trigger. That is when manufacturers dump older stock to make room for new releases, meaning last year's top-tier speed drops down to a price you can actually live with.
The 0% intro APR for 15 months on purchases and balance transfers is a deadline, not free money. If you still have a balance left when those 15 months are up, standard interest kicks in on the whole original amount.