It depends on how you're approaching the game. If you don't particularly care about getting a certain 5 or 6 star girl, there's no reason to roll the premium gacha when a team of guaranteed 5 stars, upgraded 3-4 stars, and event girls can clear all the content. Using stamina refills intelligently isn't about being impatient, it's about giving you a power spike earlier on so that you can spend more time at a stronger level, farming higher-end content sooner, which builds on itself. It's also useful to quickly get to the stage where you can leave/sleep without your stamina filling up so none is wasted. Once you reach a comfortable state, you can just sit on gems until an event or if they release a good deal in the gacha.