Depending on what you’re flying, its manufacturer may have placed specific go-around recommendations in the POH/AFM. If so, it’s always a good idea to follow them and conform to the listed sequence of actions. Going around can be a busy time, and scrounging around for the balked-landing checklist is a no-no. You should have the appropriate sequence of actions memorized from your previous landing-practice sessions.
Generally, it’s also a good idea to get the landing gear coming up first, before retracting the flaps. That’s because having the gear dangling in the breeze creates drag, reducing acceleration and climb rate. Also, the landing gear on most personal airplanes takes a few seconds to cycle from the extended position to being nicely tucked away.
A complication can arise when the gear retraction cycle momentarily creates additional drag. That can happen with some Cessna singles, when the main-gear wheels are rotated into the slipstream before being stowed in the belly. That said, leaving the gear down until everything else is resolved isn’t likely to hurt anything. The extra drag created by the extended gear is minimized by the airplane’s relatively slow speed, and the real key is maintaining control while transitioning to a climb.
The flap system also deserves consideration here. If your airplane’s flaps are electrically operated, it can take some time to retract them. Since you’re also changing the way the wings are creating lift, you might want to approach the flaps cautiously, by only retracting them to an intermediate setting. Doing so eliminates the greater drag full deployment generates while still providing some additional lift. Removing all the extra lift flaps create at a slow speed close to the ground can result in sinking back down to the runway. If the gear already is retracted…well.
Unless there’s a good reason not to, use the POH/AFM procedure. But don’t be afraid to do things a bit differently when conditions demand.